Fix PR 4626, a crash in branch folding after OptimizeBlock

produced a CFG it wasn't prepared for.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78351 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 107 insertions, 1 deletions

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index 193bbb610f..d25152b1e4 100644
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -893,8 +893,24 @@ void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
       while (!MBB->pred_empty()) {
         MachineBasicBlock *Pred = *(MBB->pred_end()-1);
         Pred->ReplaceUsesOfBlockWith(MBB, FallThrough);
+        // If this resulted in a predecessor with true and false edges
+        // both going to the fallthrough block, clean up; 
+        // BranchFolding doesn't like this.
+        MachineBasicBlock::succ_iterator SI = Pred->succ_begin();
+        bool found = false;
+        while (SI != Pred->succ_end()) {
+          if (*SI == FallThrough) {
+            if (!found) {
+              found = true;
+              ++SI;
+            } else {
+              SI = Pred->removeSuccessor(SI);
+            }
+          } else {
+            ++SI;
+          }
+        }
       }
-      
       // If MBB was the target of a jump table, update jump tables to go to the
       // fallthrough instead.
       MBB->getParent()->getJumpTableInfo()->
diff --git a/test/CodeGen/X86/2009-08-06-branchfolder-crash.ll b/test/CodeGen/X86/2009-08-06-branchfolder-crash.ll
new file mode 100644
index 0000000000..5e58725cb9
--- /dev/null
+++ b/test/CodeGen/X86/2009-08-06-branchfolder-crash.ll
@@ -0,0 +1,90 @@
+; RUN: llvm-as < %s | llc -O3
+; PR4626
+; ModuleID = '<stdin>'
+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_3 = common global i8 0, align 1		; <i8*> [#uses=2]
+
+define signext i8 @safe_mul_func_int16_t_s_s(i32 %_si1, i8 signext %_si2) nounwind readnone {
+entry:
+	%tobool = icmp eq i32 %_si1, 0		; <i1> [#uses=1]
+	%cmp = icmp sgt i8 %_si2, 0		; <i1> [#uses=2]
+	%or.cond = or i1 %cmp, %tobool		; <i1> [#uses=1]
+	br i1 %or.cond, label %lor.rhs, label %land.lhs.true3
+
+land.lhs.true3:		; preds = %entry
+	%conv5 = sext i8 %_si2 to i32		; <i32> [#uses=1]
+	%cmp7 = icmp slt i32 %conv5, %_si1		; <i1> [#uses=1]
+	br i1 %cmp7, label %cond.end, label %lor.rhs
+
+lor.rhs:		; preds = %land.lhs.true3, %entry
+	%cmp10.not = icmp slt i32 %_si1, 1		; <i1> [#uses=1]
+	%or.cond23 = and i1 %cmp, %cmp10.not		; <i1> [#uses=1]
+	br i1 %or.cond23, label %lor.end, label %cond.false
+
+lor.end:		; preds = %lor.rhs
+	%tobool19 = icmp ne i8 %_si2, 0		; <i1> [#uses=2]
+	%lor.ext = zext i1 %tobool19 to i32		; <i32> [#uses=1]
+	br i1 %tobool19, label %cond.end, label %cond.false
+
+cond.false:		; preds = %lor.end, %lor.rhs
+	%conv21 = sext i8 %_si2 to i32		; <i32> [#uses=1]
+	br label %cond.end
+
+cond.end:		; preds = %cond.false, %lor.end, %land.lhs.true3
+	%cond = phi i32 [ %conv21, %cond.false ], [ 1, %land.lhs.true3 ], [ %lor.ext, %lor.end ]		; <i32> [#uses=1]
+	%conv22 = trunc i32 %cond to i8		; <i8> [#uses=1]
+	ret i8 %conv22
+}
+
+define i32 @func_34(i8 signext %p_35) nounwind readonly {
+entry:
+	%tobool = icmp eq i8 %p_35, 0		; <i1> [#uses=1]
+	br i1 %tobool, label %lor.lhs.false, label %if.then
+
+lor.lhs.false:		; preds = %entry
+	%tmp1 = load i8* @g_3		; <i8> [#uses=1]
+	%tobool3 = icmp eq i8 %tmp1, 0		; <i1> [#uses=1]
+	br i1 %tobool3, label %return, label %if.then
+
+if.then:		; preds = %lor.lhs.false, %entry
+	%tmp4 = load i8* @g_3		; <i8> [#uses=1]
+	%conv5 = sext i8 %tmp4 to i32		; <i32> [#uses=1]
+	ret i32 %conv5
+
+return:		; preds = %lor.lhs.false
+	ret i32 0
+}
+
+define void @foo(i32 %p_5) noreturn nounwind {
+entry:
+	%cmp = icmp sgt i32 %p_5, 0		; <i1> [#uses=2]
+	%call = tail call i32 @safe() nounwind		; <i32> [#uses=1]
+	%conv1 = trunc i32 %call to i8		; <i8> [#uses=3]
+	%tobool.i = xor i1 %cmp, true		; <i1> [#uses=3]
+	%cmp.i = icmp sgt i8 %conv1, 0		; <i1> [#uses=3]
+	%or.cond.i = or i1 %cmp.i, %tobool.i		; <i1> [#uses=1]
+	br i1 %or.cond.i, label %lor.rhs.i, label %land.lhs.true3.i
+
+land.lhs.true3.i:		; preds = %entry
+	%xor = zext i1 %cmp to i32		; <i32> [#uses=1]
+	%conv5.i = sext i8 %conv1 to i32		; <i32> [#uses=1]
+	%cmp7.i = icmp slt i32 %conv5.i, %xor		; <i1> [#uses=1]
+	%cmp7.i.not = xor i1 %cmp7.i, true		; <i1> [#uses=1]
+	%or.cond23.i = and i1 %cmp.i, %tobool.i		; <i1> [#uses=1]
+	%or.cond = and i1 %cmp7.i.not, %or.cond23.i		; <i1> [#uses=1]
+	br i1 %or.cond, label %lor.end.i, label %for.inc
+
+lor.rhs.i:		; preds = %entry
+	%or.cond23.i.old = and i1 %cmp.i, %tobool.i		; <i1> [#uses=1]
+	br i1 %or.cond23.i.old, label %lor.end.i, label %for.inc
+
+lor.end.i:		; preds = %lor.rhs.i, %land.lhs.true3.i
+	%tobool19.i = icmp eq i8 %conv1, 0		; <i1> [#uses=0]
+	br label %for.inc
+
+for.inc:		; preds = %for.inc, %lor.end.i, %lor.rhs.i, %land.lhs.true3.i
+	br label %for.inc
+}
+
+declare i32 @safe()