Modify how the formulae are rated in Loop Strength Reduce.

Namely, check if the target allows to fold more that one register in the
addressing mode and if yes, adjust the cost accordingly.

Prior to this commit, reg1 + scale * reg2 accesses were artificially preferred
to reg1 + reg2 accesses. Indeed, the cost model wrongly assumed that reg1 + reg2
needs a temporary register for the computation, whereas it was correctly
estimated for reg1 + scale * reg2.

<rdar://problem/13973908>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183021 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 62 insertions, 6 deletions

diff --git a/test/Transforms/LoopStrengthReduce/2013-01-14-ReuseCast.ll b/test/Transforms/LoopStrengthReduce/2013-01-14-ReuseCast.ll
index 8fbddf8ae4..652eb06225 100644
--- a/test/Transforms/LoopStrengthReduce/2013-01-14-ReuseCast.ll
+++ b/test/Transforms/LoopStrengthReduce/2013-01-14-ReuseCast.ll
@@ -10,12 +10,12 @@ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3
 ; Verify that nothing uses the "dead" ptrtoint from "undef".
 ; CHECK: @VerifyDiagnosticConsumerTest
 ; CHECK: bb:
-; CHECK: %0 = ptrtoint i8* undef to i64
-; CHECK-NOT: %0
+; "dead" ptrpoint not emitted (or dead code eliminated) with
+; current LSR cost model.
+; CHECK-NOT: = ptrtoint i8* undef to i64
 ; CHECK: .lr.ph
-; CHECK-NOT: %0
-; CHECK: sub i64 %7, %tmp6
-; CHECK-NOT: %0
+; CHECK: [[TMP:%[^ ]+]] = add i64 %tmp5, 1
+; CHECK: sub i64 [[TMP]], %tmp6
 ; CHECK: ret void
 define void @VerifyDiagnosticConsumerTest() unnamed_addr nounwind uwtable align 2 {
 bb:
diff --git a/test/Transforms/LoopStrengthReduce/uglygep.ll b/test/Transforms/LoopStrengthReduce/uglygep.ll
index 8af5cf1dfd..10c77d5f64 100644
--- a/test/Transforms/LoopStrengthReduce/uglygep.ll
+++ b/test/Transforms/LoopStrengthReduce/uglygep.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -loop-reduce -S | not grep uglygep
+; RUN: opt < %s -loop-reduce -S | FileCheck %s
 
 ; LSR shouldn't consider %t8 to be an interesting user of %t6, and it
 ; should be able to form pretty GEPs.
@@ -6,6 +6,7 @@
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
 
 define void @Z4() nounwind {
+; CHECK: define void @Z4
 bb:
   br label %bb3
 
@@ -20,11 +21,26 @@ bb3:                                              ; preds = %bb2, %bb
   %t4 = phi i64 [ %t, %bb2 ], [ 0, %bb ]      ; <i64> [#uses=3]
   br label %bb1
 
+; CHECK: bb10:
+; CHECK-NEXT: %t7 = icmp eq i64 %t4, 0
+; Host %t2 computation outside the loop.
+; CHECK-NEXT: [[SCEVGEP:%[^ ]+]] = getelementptr i8* undef, i64 %t4
+; CHECK-NEXT: br label %bb14
 bb10:                                             ; preds = %bb9
   %t7 = icmp eq i64 %t4, 0                    ; <i1> [#uses=1]
   %t3 = add i64 %t4, 16                     ; <i64> [#uses=1]
   br label %bb14
 
+; CHECK: bb14:
+; CHECK-NEXT: store i8 undef, i8* [[SCEVGEP]]
+; CHECK-NEXT: %t6 = load float** undef
+; Fold %t3's add within the address.
+; CHECK-NEXT: [[SCEVGEP1:%[^ ]+]] = getelementptr float* %t6, i64 4
+; CHECK-NEXT: [[SCEVGEP2:%[^ ]+]] = bitcast float* [[SCEVGEP1]] to i8*
+; Use the induction variable (%t4) to access the right element
+; CHECK-NEXT: [[ADDRESS:%[^ ]+]] = getelementptr i8* [[SCEVGEP2]], i64 %t4
+; CHECK-NEXT: store i8 undef, i8* [[ADDRESS]]
+; CHECK-NEXT: br label %bb14
 bb14:                                             ; preds = %bb14, %bb10
   %t2 = getelementptr inbounds i8* undef, i64 %t4 ; <i8*> [#uses=1]
   store i8 undef, i8* %t2
@@ -36,9 +52,15 @@ bb14:                                             ; preds = %bb14, %bb10
 }
 
 define fastcc void @TransformLine() nounwind {
+; CHECK: @TransformLine
 bb:
   br label %loop0
 
+; CHECK: loop0:
+; Induction variable is initialized to -2.
+; CHECK-NEXT: [[PHIIV:%[^ ]+]] = phi i32 [ [[IVNEXT:%[^ ]+]], %loop0 ], [ -2, %bb ]
+; CHECK-NEXT: [[IVNEXT]] = add i32 [[PHIIV]], 1
+; CHECK-NEXT: br i1 false, label %loop0, label %bb0
 loop0:                                            ; preds = %loop0, %bb
   %i0 = phi i32 [ %i0.next, %loop0 ], [ 0, %bb ]  ; <i32> [#uses=2]
   %i0.next = add i32 %i0, 1                       ; <i32> [#uses=1]
@@ -47,18 +69,52 @@ loop0:                                            ; preds = %loop0, %bb
 bb0:                                              ; preds = %loop0
   br label %loop1
 
+; CHECK: loop1:
+; CHECK-NEXT: %i1 = phi i32 [ 0, %bb0 ], [ %i1.next, %bb5 ]
+; IVNEXT covers the uses of %i0 and %t0.
+; Therefore, %t0 has been removed.
+; The critical edge has been split.
+; CHECK-NEXT: br i1 false, label %bb2, label %[[LOOP1BB6:.+]]
 loop1:                                            ; preds = %bb5, %bb0
   %i1 = phi i32 [ 0, %bb0 ], [ %i1.next, %bb5 ]   ; <i32> [#uses=4]
   %t0 = add i32 %i0, %i1                          ; <i32> [#uses=1]
   br i1 false, label %bb2, label %bb6
 
+; CHECK: bb2:
+; Critical edge split.
+; CHECK-NEXT: br i1 true, label %[[BB2BB6:[^,]+]], label %bb5
 bb2:                                              ; preds = %loop1
   br i1 true, label %bb6, label %bb5
 
+; CHECK: bb5:
+; CHECK-NEXT: %i1.next = add i32 %i1, 1
+; CHECK-NEXT: br i1 true, label %[[BB5BB6:[^,]+]], label %loop1
 bb5:                                              ; preds = %bb2
   %i1.next = add i32 %i1, 1                       ; <i32> [#uses=1]
   br i1 true, label %bb6, label %loop1
 
+; bb5 to bb6 split basic block.
+; CHECK: [[BB5BB6]]:
+; CHECK-NEXT: [[INITIALVAL:%[^ ]+]] = add i32 [[IVNEXT]], %i1.next
+; CHECK-NEXT: br label %[[SPLITTOBB6:.+]]
+
+; bb2 to bb6 split basic block.
+; CHECK: [[BB2BB6]]:
+; CHECK-NEXT: br label %[[SPLITTOBB6]]
+
+; Split basic blocks to bb6.
+; CHECK: [[SPLITTOBB6]]:
+; CHECK-NEXT: [[INITP8:%[^ ]+]] = phi i32 [ [[INITIALVAL]], %[[BB5BB6]] ], [ undef, %[[BB2BB6]] ]
+; CHECK-NEXT: [[INITP9:%[^ ]+]] = phi i32 [ undef, %[[BB5BB6]] ], [ %i1, %[[BB2BB6]] ]
+; CHECK-NEXT: br label %bb6
+  
+; CHECK: [[LOOP1BB6]]:
+; CHECK-NEXT: br label %bb6
+
+; CHECK: bb6:
+; CHECK-NEXT: %p8 = phi i32 [ undef, %[[LOOP1BB6]] ], [ [[INITP8]], %[[SPLITTOBB6]] ]
+; CHECK-NEXT: %p9 = phi i32 [ %i1, %[[LOOP1BB6]] ], [ [[INITP9]], %[[SPLITTOBB6]] ]
+; CHECK-NEXT: unreachable
 bb6:                                              ; preds = %bb5, %bb2, %loop1
   %p8 = phi i32 [ %t0, %bb5 ], [ undef, %loop1 ], [ undef, %bb2 ] ; <i32> [#uses=0]
   %p9 = phi i32 [ undef, %bb5 ], [ %i1, %loop1 ], [ %i1, %bb2 ] ; <i32> [#uses=0]