Fix a bug in LSR's dead-PHI cleanup. If a PHI has a def-use chain that

leads into a cycle involving a different PHI, LSR got stuck running
around that cycle looking for the original PHI. To avoid this, keep
track of visited PHIs and stop searching if we see one more than once.
This fixes PR2570.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53879 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 290 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 5bbc8322bc..83bdb2cd17 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -1823,6 +1823,7 @@ bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
       // FIXME: this needs to eliminate an induction variable even if it's being
       // compared against some value to decide loop termination.
       if (PN->hasOneUse()) {
+        SmallPtrSet<PHINode *, 2> PHIs;
         for (Instruction *J = dyn_cast<Instruction>(*PN->use_begin());
              J && J->hasOneUse() && !J->mayWriteToMemory();
              J = dyn_cast<Instruction>(*J->use_begin())) {
@@ -1835,6 +1836,10 @@ bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
             Changed = true;
             break;
           }
+          // If we find a PHI more than once, we're on a cycle that
+          // won't prove fruitful.
+          if (isa<PHINode>(J) && !PHIs.insert(cast<PHINode>(J)))
+            break;
         }
       }
     }
diff --git a/test/Transforms/LoopStrengthReduce/pr2570.ll b/test/Transforms/LoopStrengthReduce/pr2570.ll
new file mode 100644
index 0000000000..69dc54269f
--- /dev/null
+++ b/test/Transforms/LoopStrengthReduce/pr2570.ll
@@ -0,0 +1,285 @@
+; RUN: llvm-as < %s | opt -loop-reduce | llvm-dis | grep {phi\\>} | count 14
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32"
+target triple = "i386-pc-linux-gnu"
+@g_14 = internal global i32 1		; <i32*> [#uses=1]
+@g_39 = internal global i16 -5		; <i16*> [#uses=2]
+@g_43 = internal global i32 -6		; <i32*> [#uses=3]
+@g_33 = internal global i32 -1269044541		; <i32*> [#uses=1]
+@g_137 = internal global i32 8		; <i32*> [#uses=1]
+@g_82 = internal global i32 -5		; <i32*> [#uses=3]
+@g_91 = internal global i32 1		; <i32*> [#uses=1]
+@g_197 = internal global i32 1		; <i32*> [#uses=4]
+@g_207 = internal global i32 1		; <i32*> [#uses=2]
+@g_222 = internal global i16 4165		; <i16*> [#uses=1]
+@g_247 = internal global i8 -21		; <i8*> [#uses=2]
+@g_260 = internal global i32 1		; <i32*> [#uses=2]
+@g_221 = internal global i16 -17503		; <i16*> [#uses=3]
+@g_267 = internal global i16 1		; <i16*> [#uses=1]
+@llvm.used = appending global [1 x i8*] [ i8* bitcast (i32 (i32, i32, i16, i32, i8, i32)* @func_44 to i8*) ], section "llvm.metadata"		; <[1 x i8*]*> [#uses=0]
+
+define i32 @func_44(i32 %p_45, i32 %p_46, i16 zeroext  %p_48, i32 %p_49, i8 zeroext  %p_50, i32 %p_52) nounwind  {
+entry:
+	tail call i32 @func_116( i8 zeroext  2 ) nounwind 		; <i32>:0 [#uses=0]
+	tail call i32 @func_63( i16 signext  2 ) nounwind 		; <i32>:1 [#uses=1]
+	load i16* @g_39, align 2		; <i16>:2 [#uses=1]
+	tail call i32 @func_63( i16 signext  %2 ) nounwind 		; <i32>:3 [#uses=1]
+	trunc i32 %3 to i16		; <i16>:4 [#uses=1]
+	and i16 %4, 1		; <i16>:5 [#uses=1]
+	trunc i32 %p_52 to i8		; <i8>:6 [#uses=1]
+	trunc i32 %1 to i16		; <i16>:7 [#uses=1]
+	tail call i32 @func_74( i16 zeroext  %5, i8 zeroext  %6, i16 zeroext  %7, i16 zeroext  0 ) nounwind 		; <i32>:8 [#uses=0]
+	tail call i32 @func_124( i32 544824386 ) nounwind 		; <i32>:9 [#uses=0]
+	zext i8 %p_50 to i32		; <i32>:10 [#uses=1]
+	load i32* @g_43, align 4		; <i32>:11 [#uses=1]
+	icmp sle i32 %10, %11		; <i1>:12 [#uses=1]
+	zext i1 %12 to i32		; <i32>:13 [#uses=2]
+	load i8* @g_247, align 1		; <i8>:14 [#uses=1]
+	trunc i32 %p_45 to i16		; <i16>:15 [#uses=1]
+	zext i8 %14 to i16		; <i16>:16 [#uses=1]
+	tail call i32 @func_74( i16 zeroext  %15, i8 zeroext  0, i16 zeroext  %16, i16 zeroext  23618 ) nounwind 		; <i32>:17 [#uses=4]
+	icmp slt i32 %17, 0		; <i1>:18 [#uses=1]
+	br i1 %18, label %bb162, label %bb152
+
+bb152:		; preds = %entry
+	lshr i32 2147483647, %13		; <i32>:19 [#uses=1]
+	icmp slt i32 %19, %17		; <i1>:20 [#uses=1]
+	select i1 %20, i32 0, i32 %13		; <i32>:21 [#uses=1]
+	%.348 = shl i32 %17, %21		; <i32> [#uses=1]
+	br label %bb162
+
+bb162:		; preds = %bb152, %entry
+	%.0346 = phi i32 [ %.348, %bb152 ], [ %17, %entry ]		; <i32> [#uses=1]
+	tail call i32 @func_124( i32 1 ) nounwind 		; <i32>:22 [#uses=1]
+	mul i32 %22, %.0346		; <i32>:23 [#uses=1]
+	icmp slt i32 %p_45, 0		; <i1>:24 [#uses=1]
+	icmp ugt i32 %p_45, 31		; <i1>:25 [#uses=1]
+	%or.cond = or i1 %24, %25		; <i1> [#uses=1]
+	br i1 %or.cond, label %bb172, label %bb168
+
+bb168:		; preds = %bb162
+	lshr i32 2147483647, %p_45		; <i32>:26 [#uses=1]
+	shl i32 1392859848, %p_45		; <i32>:27 [#uses=1]
+	icmp slt i32 %26, 1392859848		; <i1>:28 [#uses=1]
+	%.op355 = add i32 %27, 38978		; <i32> [#uses=1]
+	%phitmp = select i1 %28, i32 1392898826, i32 %.op355		; <i32> [#uses=1]
+	br label %bb172
+
+bb172:		; preds = %bb168, %bb162
+	%.0343 = phi i32 [ %phitmp, %bb168 ], [ 1392898826, %bb162 ]		; <i32> [#uses=2]
+	tail call i32 @func_84( i32 1, i16 zeroext  0, i16 zeroext  8 ) nounwind 		; <i32>:29 [#uses=0]
+	icmp eq i32 %.0343, 0		; <i1>:30 [#uses=1]
+	%.0341 = select i1 %30, i32 1, i32 %.0343		; <i32> [#uses=1]
+	urem i32 %23, %.0341		; <i32>:31 [#uses=1]
+	load i32* @g_137, align 4		; <i32>:32 [#uses=4]
+	icmp slt i32 %32, 0		; <i1>:33 [#uses=1]
+	br i1 %33, label %bb202, label %bb198
+
+bb198:		; preds = %bb172
+	%not. = icmp slt i32 %32, 1073741824		; <i1> [#uses=1]
+	zext i1 %not. to i32		; <i32>:34 [#uses=1]
+	%.351 = shl i32 %32, %34		; <i32> [#uses=1]
+	br label %bb202
+
+bb202:		; preds = %bb198, %bb172
+	%.0335 = phi i32 [ %.351, %bb198 ], [ %32, %bb172 ]		; <i32> [#uses=1]
+	icmp ne i32 %31, %.0335		; <i1>:35 [#uses=1]
+	zext i1 %35 to i32		; <i32>:36 [#uses=1]
+	tail call i32 @func_128( i32 %36 ) nounwind 		; <i32>:37 [#uses=0]
+	icmp eq i32 %p_45, 293685862		; <i1>:38 [#uses=1]
+	br i1 %38, label %bb205, label %bb311
+
+bb205:		; preds = %bb202
+	icmp sgt i32 %p_46, 214		; <i1>:39 [#uses=1]
+	zext i1 %39 to i32		; <i32>:40 [#uses=2]
+	tail call i32 @func_128( i32 %40 ) nounwind 		; <i32>:41 [#uses=0]
+	icmp sgt i32 %p_46, 65532		; <i1>:42 [#uses=1]
+	zext i1 %42 to i16		; <i16>:43 [#uses=1]
+	tail call i32 @func_74( i16 zeroext  23618, i8 zeroext  -29, i16 zeroext  %43, i16 zeroext  1 ) nounwind 		; <i32>:44 [#uses=2]
+	tail call i32 @func_103( i16 zeroext  -869 ) nounwind 		; <i32>:45 [#uses=0]
+	udiv i32 %44, 34162		; <i32>:46 [#uses=1]
+	icmp ult i32 %44, 34162		; <i1>:47 [#uses=1]
+	%.0331 = select i1 %47, i32 1, i32 %46		; <i32> [#uses=1]
+	urem i32 293685862, %.0331		; <i32>:48 [#uses=1]
+	tail call i32 @func_112( i32 %p_52, i16 zeroext  1 ) nounwind 		; <i32>:49 [#uses=0]
+	icmp eq i32 %p_52, 0		; <i1>:50 [#uses=2]
+	br i1 %50, label %bb222, label %bb215
+
+bb215:		; preds = %bb205
+	zext i16 %p_48 to i32		; <i32>:51 [#uses=1]
+	icmp eq i16 %p_48, 0		; <i1>:52 [#uses=1]
+	%.0329 = select i1 %52, i32 1, i32 %51		; <i32> [#uses=1]
+	udiv i32 -1, %.0329		; <i32>:53 [#uses=1]
+	icmp eq i32 %53, 0		; <i1>:54 [#uses=1]
+	br i1 %54, label %bb222, label %bb223
+
+bb222:		; preds = %bb215, %bb205
+	br label %bb223
+
+bb223:		; preds = %bb222, %bb215
+	%iftmp.437.0 = phi i32 [ 0, %bb222 ], [ 1, %bb215 ]		; <i32> [#uses=1]
+	load i32* @g_91, align 4		; <i32>:55 [#uses=3]
+	tail call i32 @func_103( i16 zeroext  4 ) nounwind 		; <i32>:56 [#uses=0]
+	tail call i32 @func_112( i32 0, i16 zeroext  -31374 ) nounwind 		; <i32>:57 [#uses=0]
+	load i32* @g_197, align 4		; <i32>:58 [#uses=1]
+	tail call i32 @func_124( i32 28156 ) nounwind 		; <i32>:59 [#uses=1]
+	load i32* @g_260, align 4		; <i32>:60 [#uses=1]
+	load i32* @g_43, align 4		; <i32>:61 [#uses=1]
+	xor i32 %61, %60		; <i32>:62 [#uses=1]
+	mul i32 %62, %59		; <i32>:63 [#uses=1]
+	trunc i32 %63 to i8		; <i8>:64 [#uses=1]
+	trunc i32 %58 to i16		; <i16>:65 [#uses=1]
+	tail call i32 @func_74( i16 zeroext  0, i8 zeroext  %64, i16 zeroext  %65, i16 zeroext  0 ) nounwind 		; <i32>:66 [#uses=2]
+	icmp slt i32 %66, 0		; <i1>:67 [#uses=1]
+	icmp slt i32 %55, 0		; <i1>:68 [#uses=1]
+	icmp ugt i32 %55, 31		; <i1>:69 [#uses=1]
+	or i1 %68, %69		; <i1>:70 [#uses=1]
+	%or.cond352 = or i1 %70, %67		; <i1> [#uses=1]
+	select i1 %or.cond352, i32 0, i32 %55		; <i32>:71 [#uses=1]
+	%.353 = ashr i32 %66, %71		; <i32> [#uses=2]
+	load i16* @g_221, align 2		; <i16>:72 [#uses=1]
+	zext i16 %72 to i32		; <i32>:73 [#uses=1]
+	icmp ugt i32 %.353, 31		; <i1>:74 [#uses=1]
+	select i1 %74, i32 0, i32 %.353		; <i32>:75 [#uses=1]
+	%.0323 = lshr i32 %73, %75		; <i32> [#uses=1]
+	add i32 %.0323, %iftmp.437.0		; <i32>:76 [#uses=1]
+	and i32 %48, 255		; <i32>:77 [#uses=2]
+	add i32 %77, 2042556439		; <i32>:78 [#uses=1]
+	load i32* @g_207, align 4		; <i32>:79 [#uses=2]
+	icmp ugt i32 %79, 31		; <i1>:80 [#uses=1]
+	select i1 %80, i32 0, i32 %79		; <i32>:81 [#uses=1]
+	%.0320 = lshr i32 %77, %81		; <i32> [#uses=1]
+	icmp ne i32 %78, %.0320		; <i1>:82 [#uses=1]
+	zext i1 %82 to i8		; <i8>:83 [#uses=1]
+	tail call i32 @func_25( i8 zeroext  %83 ) nounwind 		; <i32>:84 [#uses=1]
+	xor i32 %84, 1		; <i32>:85 [#uses=1]
+	load i32* @g_197, align 4		; <i32>:86 [#uses=1]
+	add i32 %86, 1		; <i32>:87 [#uses=1]
+	add i32 %87, %85		; <i32>:88 [#uses=1]
+	icmp ugt i32 %76, %88		; <i1>:89 [#uses=1]
+	br i1 %89, label %bb241, label %bb311
+
+bb241:		; preds = %bb223
+	store i16 -9, i16* @g_221, align 2
+	udiv i32 %p_52, 1538244727		; <i32>:90 [#uses=1]
+	load i32* @g_207, align 4		; <i32>:91 [#uses=1]
+	sub i32 %91, %90		; <i32>:92 [#uses=1]
+	load i32* @g_14, align 4		; <i32>:93 [#uses=1]
+	trunc i32 %93 to i16		; <i16>:94 [#uses=1]
+	trunc i32 %p_46 to i16		; <i16>:95 [#uses=2]
+	sub i16 %94, %95		; <i16>:96 [#uses=1]
+	load i32* @g_197, align 4		; <i32>:97 [#uses=1]
+	trunc i32 %97 to i16		; <i16>:98 [#uses=1]
+	tail call i32 @func_55( i32 -346178830, i16 zeroext  %98, i16 zeroext  %95 ) nounwind 		; <i32>:99 [#uses=0]
+	zext i16 %p_48 to i32		; <i32>:100 [#uses=1]
+	load i8* @g_247, align 1		; <i8>:101 [#uses=1]
+	zext i8 %101 to i32		; <i32>:102 [#uses=1]
+	sub i32 %100, %102		; <i32>:103 [#uses=1]
+	tail call i32 @func_55( i32 %103, i16 zeroext  -2972, i16 zeroext  %96 ) nounwind 		; <i32>:104 [#uses=0]
+	xor i32 %92, 2968		; <i32>:105 [#uses=1]
+	load i32* @g_197, align 4		; <i32>:106 [#uses=1]
+	icmp ugt i32 %105, %106		; <i1>:107 [#uses=1]
+	zext i1 %107 to i32		; <i32>:108 [#uses=1]
+	store i32 %108, i32* @g_33, align 4
+	br label %bb248
+
+bb248:		; preds = %bb284, %bb241
+	%p_49_addr.1.reg2mem.0 = phi i32 [ 0, %bb241 ], [ %134, %bb284 ]		; <i32> [#uses=2]
+	%p_48_addr.2.reg2mem.0 = phi i16 [ %p_48, %bb241 ], [ %p_48_addr.1, %bb284 ]		; <i16> [#uses=1]
+	%p_46_addr.1.reg2mem.0 = phi i32 [ %p_46, %bb241 ], [ %133, %bb284 ]		; <i32> [#uses=1]
+	%p_45_addr.1.reg2mem.0 = phi i32 [ %p_45, %bb241 ], [ %p_45_addr.0, %bb284 ]		; <i32> [#uses=2]
+	tail call i32 @func_63( i16 signext  1 ) nounwind 		; <i32>:109 [#uses=1]
+	icmp eq i32 %109, 0		; <i1>:110 [#uses=1]
+	br i1 %110, label %bb272.thread, label %bb255.thread
+
+bb272.thread:		; preds = %bb248
+	store i32 1, i32* @g_82
+	load i16* @g_267, align 2		; <i16>:111 [#uses=1]
+	icmp eq i16 %111, 0		; <i1>:112 [#uses=1]
+	br i1 %112, label %bb311.loopexit.split, label %bb268
+
+bb255.thread:		; preds = %bb248
+	load i32* @g_260, align 4		; <i32>:113 [#uses=1]
+	sub i32 %113, %p_52		; <i32>:114 [#uses=1]
+	and i32 %114, -20753		; <i32>:115 [#uses=1]
+	icmp ne i32 %115, 0		; <i1>:116 [#uses=1]
+	zext i1 %116 to i16		; <i16>:117 [#uses=1]
+	store i16 %117, i16* @g_221, align 2
+	br label %bb284
+
+bb268:		; preds = %bb268, %bb272.thread
+	%indvar = phi i32 [ 0, %bb272.thread ], [ %g_82.tmp.0, %bb268 ]		; <i32> [#uses=2]
+	%p_46_addr.0.reg2mem.0 = phi i32 [ %p_46_addr.1.reg2mem.0, %bb272.thread ], [ %119, %bb268 ]		; <i32> [#uses=1]
+	%g_82.tmp.0 = add i32 %indvar, 1		; <i32> [#uses=2]
+	trunc i32 %p_46_addr.0.reg2mem.0 to i16		; <i16>:118 [#uses=1]
+	and i32 %g_82.tmp.0, 28156		; <i32>:119 [#uses=1]
+	add i32 %indvar, 2		; <i32>:120 [#uses=4]
+	icmp sgt i32 %120, -1		; <i1>:121 [#uses=1]
+	br i1 %121, label %bb268, label %bb274.split
+
+bb274.split:		; preds = %bb268
+	store i32 %120, i32* @g_82
+	br i1 %50, label %bb279, label %bb276
+
+bb276:		; preds = %bb274.split
+	store i16 0, i16* @g_222, align 2
+	br label %bb284
+
+bb279:		; preds = %bb274.split
+	icmp eq i32 %120, 0		; <i1>:122 [#uses=1]
+	%.0317 = select i1 %122, i32 1, i32 %120		; <i32> [#uses=1]
+	udiv i32 -8, %.0317		; <i32>:123 [#uses=1]
+	trunc i32 %123 to i16		; <i16>:124 [#uses=1]
+	br label %bb284
+
+bb284:		; preds = %bb279, %bb276, %bb255.thread
+	%p_49_addr.0 = phi i32 [ %p_49_addr.1.reg2mem.0, %bb279 ], [ %p_49_addr.1.reg2mem.0, %bb276 ], [ 0, %bb255.thread ]		; <i32> [#uses=1]
+	%p_48_addr.1 = phi i16 [ %124, %bb279 ], [ %118, %bb276 ], [ %p_48_addr.2.reg2mem.0, %bb255.thread ]		; <i16> [#uses=1]
+	%p_45_addr.0 = phi i32 [ %p_45_addr.1.reg2mem.0, %bb279 ], [ %p_45_addr.1.reg2mem.0, %bb276 ], [ 8, %bb255.thread ]		; <i32> [#uses=3]
+	load i32* @g_43, align 4		; <i32>:125 [#uses=1]
+	trunc i32 %125 to i8		; <i8>:126 [#uses=1]
+	tail call i32 @func_116( i8 zeroext  %126 ) nounwind 		; <i32>:127 [#uses=0]
+	lshr i32 65255, %p_45_addr.0		; <i32>:128 [#uses=1]
+	icmp ugt i32 %p_45_addr.0, 31		; <i1>:129 [#uses=1]
+	%.op = lshr i32 %128, 31		; <i32> [#uses=1]
+	%.op.op = xor i32 %.op, 1		; <i32> [#uses=1]
+	%.354..lobit.not = select i1 %129, i32 1, i32 %.op.op		; <i32> [#uses=1]
+	load i16* @g_39, align 2		; <i16>:130 [#uses=1]
+	zext i16 %130 to i32		; <i32>:131 [#uses=1]
+	icmp slt i32 %.354..lobit.not, %131		; <i1>:132 [#uses=1]
+	zext i1 %132 to i32		; <i32>:133 [#uses=1]
+	add i32 %p_49_addr.0, 1		; <i32>:134 [#uses=2]
+	icmp sgt i32 %134, -1		; <i1>:135 [#uses=1]
+	br i1 %135, label %bb248, label %bb307
+
+bb307:		; preds = %bb284
+	tail call i32 @func_103( i16 zeroext  0 ) nounwind 		; <i32>:136 [#uses=0]
+	ret i32 %40
+
+bb311.loopexit.split:		; preds = %bb272.thread
+	store i32 1, i32* @g_82
+	ret i32 1
+
+bb311:		; preds = %bb223, %bb202
+	%.0 = phi i32 [ 1, %bb202 ], [ 0, %bb223 ]		; <i32> [#uses=1]
+	ret i32 %.0
+}
+
+declare i32 @func_25(i8 zeroext ) nounwind 
+
+declare i32 @func_55(i32, i16 zeroext , i16 zeroext ) nounwind 
+
+declare i32 @func_63(i16 signext ) nounwind 
+
+declare i32 @func_74(i16 zeroext , i8 zeroext , i16 zeroext , i16 zeroext ) nounwind 
+
+declare i32 @func_84(i32, i16 zeroext , i16 zeroext ) nounwind 
+
+declare i32 @func_103(i16 zeroext ) nounwind 
+
+declare i32 @func_124(i32) nounwind 
+
+declare i32 @func_128(i32) nounwind 
+
+declare i32 @func_116(i8 zeroext ) nounwind 
+
+declare i32 @func_112(i32, i16 zeroext ) nounwind