[llvm] 5ff35ba - [AMDGPU][GlobalISel] Fix insert point in FoldableFneg combine

[Mirko Brkusanin via llvm-commits]

Author: Mirko Brkusanin
Date: 2022-02-11T12:09:40+01:00
New Revision: 5ff35ba8ae3cb2995ee29961b852b18168776d94

URL: https://github.com/llvm/llvm-project/commit/5ff35ba8ae3cb2995ee29961b852b18168776d94
DIFF: https://github.com/llvm/llvm-project/commit/5ff35ba8ae3cb2995ee29961b852b18168776d94.diff

LOG: [AMDGPU][GlobalISel] Fix insert point in FoldableFneg combine

Newly created fneg was built after some of it's uses in some cases.
Now it will be built immediately after instruction whose dst it negates.

Differential Revision: https://reviews.llvm.org/D119459

Added: 
    

Modified: 
    llvm/lib/Target/AMDGPU/AMDGPUCombinerHelper.cpp
    llvm/test/CodeGen/AMDGPU/GlobalISel/combine-foldable-fneg.mir

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AMDGPU/AMDGPUCombinerHelper.cpp b/llvm/lib/Target/AMDGPU/AMDGPUCombinerHelper.cpp
index e79ff9b597c92..c16d8ee51a7af 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUCombinerHelper.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUCombinerHelper.cpp
@@ -373,7 +373,8 @@ void AMDGPUCombinerHelper::applyFoldableFneg(MachineInstr &MI,
     replaceRegWith(MRI, Dst, NegatedMatchInfo);
 
     // Recreate non negated value for other uses of old MatchInfoDst
-    Builder.setInstrAndDebugLoc(MI);
+    auto NextInst = ++MatchInfo->getIterator();
+    Builder.setInstrAndDebugLoc(*NextInst);
     Builder.buildFNeg(MatchInfoDst, NegatedMatchInfo, MI.getFlags());
   }
 

diff  --git a/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-foldable-fneg.mir b/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-foldable-fneg.mir
index 093cd0d5c73c6..c305727512a15 100644
--- a/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-foldable-fneg.mir
+++ b/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-foldable-fneg.mir
@@ -777,3 +777,31 @@ body:             |
     $vgpr2 = COPY %7:_(s32)
 
 ...
+
+# Check if new fneg is inserted at the appropriate place
+---
+name:            fneg_src_has_multiple_uses
+body:             |
+  bb.0:
+    liveins: $vgpr0, $vgpr1, $vgpr2
+
+    ; CHECK-LABEL: name: fneg_src_has_multiple_uses
+    ; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $vgpr0
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:_(s32) = COPY $vgpr1
+    ; CHECK-NEXT: [[COPY2:%[0-9]+]]:_(s32) = COPY $vgpr2
+    ; CHECK-NEXT: [[FNEG:%[0-9]+]]:_(s32) = G_FNEG [[COPY1]]
+    ; CHECK-NEXT: [[FMUL:%[0-9]+]]:_(s32) = G_FMUL [[COPY]], [[FNEG]]
+    ; CHECK-NEXT: [[FNEG1:%[0-9]+]]:_(s32) = G_FNEG [[FMUL]]
+    ; CHECK-NEXT: [[FMUL1:%[0-9]+]]:_(s32) = G_FMUL [[FNEG1]], [[COPY2]]
+    ; CHECK-NEXT: $vgpr0 = COPY [[FMUL1]](s32)
+    ; CHECK-NEXT: $vgpr1 = COPY [[FMUL]](s32)
+    %0:_(s32) = COPY $vgpr0
+    %1:_(s32) = COPY $vgpr1
+    %2:_(s32) = COPY $vgpr2
+    %3:_(s32) = G_FMUL %0:_, %1:_
+    %4:_(s32) = G_FMUL %3:_, %2:_
+    %5:_(s32) = G_FNEG %3:_
+    $vgpr0 = COPY %4:_(s32)
+    $vgpr1 = COPY %5:_(s32)
+
+...