[llvm] [InstSimplify] Fix incorrect poison propagation when folding phi (PR #96631)

via llvm-commits llvm-commits at lists.llvm.org
Tue Jun 25 06:07:46 PDT 2024


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Nikita Popov (nikic)

<details>
<summary>Changes</summary>

We can only replace phi(X, undef) with X, if X is known not to be poison. Otherwise, the result may be more poisonous on the undef branch.

---

Patch is 23.22 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/96631.diff


13 Files Affected:

- (modified) llvm/lib/Analysis/InstructionSimplify.cpp (+8-1) 
- (modified) llvm/test/CodeGen/AArch64/convertphitype.ll (+3-2) 
- (modified) llvm/test/CodeGen/AArch64/sve-breakdown-scalable-vectortype.ll (+21-21) 
- (modified) llvm/test/CodeGen/Hexagon/frame-offset-overflow.ll (+1-1) 
- (modified) llvm/test/CodeGen/Hexagon/trunc-mpy.ll (+1-1) 
- (modified) llvm/test/CodeGen/PowerPC/sms-phi-5.ll (+1-1) 
- (modified) llvm/test/Transforms/IndVarSimplify/invalidate-modified-lcssa-phi.ll (+4-3) 
- (modified) llvm/test/Transforms/InstCombine/phi.ll (+2-1) 
- (modified) llvm/test/Transforms/InstSimplify/phi.ll (+2-1) 
- (modified) llvm/test/Transforms/LoopDeletion/pr53969.ll (+1-1) 
- (modified) llvm/test/Transforms/LoopStrengthReduce/X86/2012-01-13-phielim.ll (+12-12) 
- (modified) llvm/test/Transforms/LoopVectorize/pr31190.ll (+2-2) 
- (modified) llvm/test/Transforms/LoopVectorize/uniform-blend.ll (+10-10) 


``````````diff
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index a452add93a7e7..c5fea8f93ef93 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -5278,7 +5278,14 @@ static Value *simplifyPHINode(PHINode *PN, ArrayRef<Value *> IncomingValues,
     // If we have a PHI node like phi(X, undef, X), where X is defined by some
     // instruction, we cannot return X as the result of the PHI node unless it
     // dominates the PHI block.
-    return valueDominatesPHI(CommonValue, PN, Q.DT) ? CommonValue : nullptr;
+    if (!valueDominatesPHI(CommonValue, PN, Q.DT))
+      return nullptr;
+
+    // Make sure we do not replace an undef value with poison.
+    if (HasUndefInput &&
+        !isGuaranteedNotToBePoison(CommonValue, Q.AC, Q.CxtI, Q.DT))
+      return nullptr;
+    return CommonValue;
   }
 
   return CommonValue;
diff --git a/llvm/test/CodeGen/AArch64/convertphitype.ll b/llvm/test/CodeGen/AArch64/convertphitype.ll
index b723b470266a7..e690653237a2d 100644
--- a/llvm/test/CodeGen/AArch64/convertphitype.ll
+++ b/llvm/test/CodeGen/AArch64/convertphitype.ll
@@ -341,6 +341,7 @@ define float @convphi_loopdelayed(ptr %s, ptr %d, i64 %n) {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[CMP15:%.*]] = icmp sgt i64 [[N:%.*]], 0
 ; CHECK-NEXT:    [[LS:%.*]] = load i32, ptr [[S:%.*]], align 4
+; CHECK-NEXT:    [[LS_BC:%.*]] = bitcast i32 [[LS]] to float
 ; CHECK-NEXT:    br i1 [[CMP15]], label [[LOOP:%.*]], label [[END:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
@@ -349,8 +350,8 @@ define float @convphi_loopdelayed(ptr %s, ptr %d, i64 %n) {
 ; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i64 [[IV_NEXT]], [[N]]
 ; CHECK-NEXT:    br i1 [[EXITCOND]], label [[END]], label [[LOOP]]
 ; CHECK:       end:
-; CHECK-NEXT:    [[B:%.*]] = bitcast i32 [[LS]] to float
-; CHECK-NEXT:    ret float [[B]]
+; CHECK-NEXT:    [[PHI_TC:%.*]] = phi float [ undef, [[ENTRY]] ], [ [[LS_BC]], [[LOOP]] ]
+; CHECK-NEXT:    ret float [[PHI_TC]]
 ;
 entry:
   %cmp15 = icmp sgt i64 %n, 0
diff --git a/llvm/test/CodeGen/AArch64/sve-breakdown-scalable-vectortype.ll b/llvm/test/CodeGen/AArch64/sve-breakdown-scalable-vectortype.ll
index 5b69b68552a4d..3645af3ccaee0 100644
--- a/llvm/test/CodeGen/AArch64/sve-breakdown-scalable-vectortype.ll
+++ b/llvm/test/CodeGen/AArch64/sve-breakdown-scalable-vectortype.ll
@@ -33,7 +33,7 @@ define <vscale x 32 x i8> @wide_32i8(i1 %b, <vscale x 16 x i8> %legal, <vscale x
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 32 x i8> undef
+  ret <vscale x 32 x i8> poison
 L2:
   ret <vscale x 32 x i8> %illegal
 }
@@ -61,7 +61,7 @@ define <vscale x 16 x i16> @wide_16i16(i1 %b, <vscale x 16 x i8> %legal, <vscale
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 16 x i16> undef
+  ret <vscale x 16 x i16> poison
 L2:
   ret <vscale x 16 x i16> %illegal
 }
@@ -89,7 +89,7 @@ define <vscale x 8 x i32> @wide_8i32(i1 %b, <vscale x 16 x i8> %legal, <vscale x
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 8 x i32> undef
+  ret <vscale x 8 x i32> poison
 L2:
   ret <vscale x 8 x i32> %illegal
 }
@@ -117,7 +117,7 @@ define <vscale x 4 x i64> @wide_4i64(i1 %b, <vscale x 16 x i8> %legal, <vscale x
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 4 x i64> undef
+  ret <vscale x 4 x i64> poison
 L2:
   ret <vscale x 4 x i64> %illegal
 }
@@ -145,7 +145,7 @@ define <vscale x 16 x half> @wide_16f16(i1 %b, <vscale x 16 x i8> %legal, <vscal
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 16 x half> undef
+  ret <vscale x 16 x half> poison
 L2:
   ret <vscale x 16 x half> %illegal
 }
@@ -173,7 +173,7 @@ define <vscale x 8 x float> @wide_8f32(i1 %b, <vscale x 16 x i8> %legal, <vscale
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 8 x float> undef
+  ret <vscale x 8 x float> poison
 L2:
   ret <vscale x 8 x float> %illegal
 }
@@ -201,7 +201,7 @@ define <vscale x 4 x double> @wide_4f64(i1 %b, <vscale x 16 x i8> %legal, <vscal
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 4 x double> undef
+  ret <vscale x 4 x double> poison
 L2:
   ret <vscale x 4 x double> %illegal
 }
@@ -237,7 +237,7 @@ define <vscale x 48 x i8> @wide_48i8(i1 %b, <vscale x 16 x i8> %legal, <vscale x
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 48 x i8> undef
+  ret <vscale x 48 x i8> poison
 L2:
   ret <vscale x 48 x i8> %illegal
 }
@@ -269,7 +269,7 @@ define <vscale x 24 x i16> @wide_24i16(i1 %b, <vscale x 16 x i8> %legal, <vscale
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 24 x i16> undef
+  ret <vscale x 24 x i16> poison
 L2:
   ret <vscale x 24 x i16> %illegal
 }
@@ -301,7 +301,7 @@ define <vscale x 12 x i32> @wide_12i32(i1 %b, <vscale x 16 x i8> %legal, <vscale
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 12 x i32> undef
+  ret <vscale x 12 x i32> poison
 L2:
   ret <vscale x 12 x i32> %illegal
 }
@@ -333,7 +333,7 @@ define <vscale x 6 x i64> @wide_6i64(i1 %b, <vscale x 16 x i8> %legal, <vscale x
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 6 x i64> undef
+  ret <vscale x 6 x i64> poison
 L2:
   ret <vscale x 6 x i64> %illegal
 }
@@ -365,7 +365,7 @@ define <vscale x 24 x half> @wide_24f16(i1 %b, <vscale x 16 x i8> %legal, <vscal
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 24 x half> undef
+  ret <vscale x 24 x half> poison
 L2:
   ret <vscale x 24 x half> %illegal
 }
@@ -397,7 +397,7 @@ define <vscale x 12 x float> @wide_12f32(i1 %b, <vscale x 16 x i8> %legal, <vsca
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 12 x float> undef
+  ret <vscale x 12 x float> poison
 L2:
   ret <vscale x 12 x float> %illegal
 }
@@ -429,7 +429,7 @@ define <vscale x 6 x double> @wide_6f64(i1 %b, <vscale x 16 x i8> %legal, <vscal
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 6 x double> undef
+  ret <vscale x 6 x double> poison
 L2:
   ret <vscale x 6 x double> %illegal
 }
@@ -469,7 +469,7 @@ define <vscale x 64 x i8> @wide_64i8(i1 %b, <vscale x 16 x i8> %legal, <vscale x
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 64 x i8> undef
+  ret <vscale x 64 x i8> poison
 L2:
   ret <vscale x 64 x i8> %illegal
 }
@@ -505,7 +505,7 @@ define <vscale x 32 x i16> @wide_32i16(i1 %b, <vscale x 16 x i8> %legal, <vscale
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 32 x i16> undef
+  ret <vscale x 32 x i16> poison
 L2:
   ret <vscale x 32 x i16> %illegal
 }
@@ -541,7 +541,7 @@ define <vscale x 16 x i32> @wide_16i32(i1 %b, <vscale x 16 x i8> %legal, <vscale
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 16 x i32> undef
+  ret <vscale x 16 x i32> poison
 L2:
   ret <vscale x 16 x i32> %illegal
 }
@@ -577,7 +577,7 @@ define <vscale x 8 x i64> @wide_8i64(i1 %b, <vscale x 16 x i8> %legal, <vscale x
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 8 x i64> undef
+  ret <vscale x 8 x i64> poison
 L2:
   ret <vscale x 8 x i64> %illegal
 }
@@ -613,7 +613,7 @@ define <vscale x 32 x half> @wide_32f16(i1 %b, <vscale x 16 x i8> %legal, <vscal
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 32 x half> undef
+  ret <vscale x 32 x half> poison
 L2:
   ret <vscale x 32 x half> %illegal
 }
@@ -649,7 +649,7 @@ define <vscale x 16 x float> @wide_16f32(i1 %b, <vscale x 16 x i8> %legal, <vsca
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 16 x float> undef
+  ret <vscale x 16 x float> poison
 L2:
   ret <vscale x 16 x float> %illegal
 }
@@ -685,7 +685,7 @@ define <vscale x 8 x double> @wide_8f64(i1 %b, <vscale x 16 x i8> %legal, <vscal
   br i1 %b, label %L1, label %L2
 L1:
   call aarch64_sve_vector_pcs void @bar()
-  ret <vscale x 8 x double> undef
+  ret <vscale x 8 x double> poison
 L2:
   ret <vscale x 8 x double> %illegal
 }
diff --git a/llvm/test/CodeGen/Hexagon/frame-offset-overflow.ll b/llvm/test/CodeGen/Hexagon/frame-offset-overflow.ll
index 861a54f893f0f..8b10305497503 100644
--- a/llvm/test/CodeGen/Hexagon/frame-offset-overflow.ll
+++ b/llvm/test/CodeGen/Hexagon/frame-offset-overflow.ll
@@ -34,7 +34,7 @@ for.body:                                         ; preds = %for.body, %entry
   %optr.0102 = phi ptr [ %incdec.ptr24.3, %for.body ], [ %p3, %entry ]
   %iptr4.0101 = phi ptr [ %incdec.ptr23.3, %for.body ], [ %incdec.ptr18, %entry ]
   %iptr3.0100 = phi ptr [ %incdec.ptr22.3, %for.body ], [ %incdec.ptr17, %entry ]
-  %iptr2.099 = phi ptr [ undef, %for.body ], [ %incdec.ptr16, %entry ]
+  %iptr2.099 = phi ptr [ poison, %for.body ], [ %incdec.ptr16, %entry ]
   %iptr1.098 = phi ptr [ %incdec.ptr20.3, %for.body ], [ %incdec.ptr15, %entry ]
   %iptr0.097 = phi ptr [ %incdec.ptr19.3, %for.body ], [ %incdec.ptr, %entry ]
   %dVsumv1.096 = phi <32 x i32> [ %60, %for.body ], [ undef, %entry ]
diff --git a/llvm/test/CodeGen/Hexagon/trunc-mpy.ll b/llvm/test/CodeGen/Hexagon/trunc-mpy.ll
index ee2a85008019e..ea132495cde85 100644
--- a/llvm/test/CodeGen/Hexagon/trunc-mpy.ll
+++ b/llvm/test/CodeGen/Hexagon/trunc-mpy.ll
@@ -69,7 +69,7 @@ b1:                                               ; preds = %b0
 
 b2:                                               ; preds = %b2, %b1
   %v2 = phi ptr [ %v0, %b1 ], [ %v14, %b2 ]
-  %v3 = phi ptr [ %v1, %b1 ], [ undef, %b2 ]
+  %v3 = phi ptr [ %v1, %b1 ], [ poison, %b2 ]
   %v4 = phi ptr [ null, %b1 ], [ %v6, %b2 ]
   %v5 = load i32, ptr %v4, align 4
   %v6 = getelementptr inbounds i32, ptr %v4, i32 2
diff --git a/llvm/test/CodeGen/PowerPC/sms-phi-5.ll b/llvm/test/CodeGen/PowerPC/sms-phi-5.ll
index 5a4aa8fdfbf39..5dcfdf5cc8124 100644
--- a/llvm/test/CodeGen/PowerPC/sms-phi-5.ll
+++ b/llvm/test/CodeGen/PowerPC/sms-phi-5.ll
@@ -35,7 +35,7 @@ define void @phi5() unnamed_addr {
   %4 = phi i16 [ %18, %3 ], [ undef, %1 ]
   %5 = phi i16 [ %13, %3 ], [ undef, %1 ]
   %6 = phi i16 [ %11, %3 ], [ undef, %1 ]
-  %7 = phi i16 [ undef, %3 ], [ %2, %1 ]
+  %7 = phi i16 [ poison, %3 ], [ %2, %1 ]
   %8 = phi i32 [ %19, %3 ], [ undef, %1 ]
   %9 = lshr i16 %6, 1
   %10 = shl i16 %7, 15
diff --git a/llvm/test/Transforms/IndVarSimplify/invalidate-modified-lcssa-phi.ll b/llvm/test/Transforms/IndVarSimplify/invalidate-modified-lcssa-phi.ll
index 856fc37620499..4833d22de07b5 100644
--- a/llvm/test/Transforms/IndVarSimplify/invalidate-modified-lcssa-phi.ll
+++ b/llvm/test/Transforms/IndVarSimplify/invalidate-modified-lcssa-phi.ll
@@ -47,17 +47,18 @@ define i8 @test_pr52023(i1 %c.1, i1 %c.2) {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br label [[LOOP_1:%.*]]
 ; CHECK:       loop.1:
-; CHECK-NEXT:    [[INC79:%.*]] = phi i8 [ [[TMP0:%.*]], [[LOOP_1_LATCH:%.*]] ], [ 0, [[ENTRY:%.*]] ]
-; CHECK-NEXT:    [[TMP0]] = add i8 [[INC79]], 1
+; CHECK-NEXT:    [[INC79:%.*]] = phi i8 [ [[INC_LCSSA:%.*]], [[LOOP_1_LATCH:%.*]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = add i8 [[INC79]], 1
 ; CHECK-NEXT:    br label [[LOOP_2:%.*]]
 ; CHECK:       loop.2:
 ; CHECK-NEXT:    br i1 [[C_1:%.*]], label [[LOOP_2_LATCH:%.*]], label [[LOOP_1_LATCH]]
 ; CHECK:       loop.2.latch:
 ; CHECK-NEXT:    br label [[LOOP_1_LATCH]]
 ; CHECK:       loop.1.latch:
+; CHECK-NEXT:    [[INC_LCSSA]] = phi i8 [ [[TMP0]], [[LOOP_2_LATCH]] ], [ undef, [[LOOP_2]] ]
 ; CHECK-NEXT:    br i1 [[C_2:%.*]], label [[EXIT:%.*]], label [[LOOP_1]]
 ; CHECK:       exit:
-; CHECK-NEXT:    [[INC_LCSSA_LCSSA:%.*]] = phi i8 [ [[TMP0]], [[LOOP_1_LATCH]] ]
+; CHECK-NEXT:    [[INC_LCSSA_LCSSA:%.*]] = phi i8 [ [[INC_LCSSA]], [[LOOP_1_LATCH]] ]
 ; CHECK-NEXT:    ret i8 [[INC_LCSSA_LCSSA]]
 ;
 entry:
diff --git a/llvm/test/Transforms/InstCombine/phi.ll b/llvm/test/Transforms/InstCombine/phi.ll
index b12982dd27e40..0ffd7b237e762 100644
--- a/llvm/test/Transforms/InstCombine/phi.ll
+++ b/llvm/test/Transforms/InstCombine/phi.ll
@@ -93,9 +93,10 @@ define i32 @test5_undef(i32 %A, i1 %cond) {
 ; CHECK-NEXT:  BB0:
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       Loop:
+; CHECK-NEXT:    [[B:%.*]] = phi i32 [ [[A:%.*]], [[BB0:%.*]] ], [ undef, [[LOOP]] ]
 ; CHECK-NEXT:    br i1 [[COND:%.*]], label [[LOOP]], label [[EXIT:%.*]]
 ; CHECK:       Exit:
-; CHECK-NEXT:    ret i32 [[A:%.*]]
+; CHECK-NEXT:    ret i32 [[B]]
 ;
 BB0:
   br label %Loop
diff --git a/llvm/test/Transforms/InstSimplify/phi.ll b/llvm/test/Transforms/InstSimplify/phi.ll
index 5cc3fecb129f4..496a3c896944b 100644
--- a/llvm/test/Transforms/InstSimplify/phi.ll
+++ b/llvm/test/Transforms/InstSimplify/phi.ll
@@ -81,7 +81,8 @@ define i32 @undef(i1 %cond, i32 %v) {
 ; CHECK:       B:
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       EXIT:
-; CHECK-NEXT:    ret i32 [[V:%.*]]
+; CHECK-NEXT:    [[W:%.*]] = phi i32 [ [[V:%.*]], [[A]] ], [ undef, [[B]] ]
+; CHECK-NEXT:    ret i32 [[W]]
 ;
   br i1 %cond, label %A, label %B
 A:
diff --git a/llvm/test/Transforms/LoopDeletion/pr53969.ll b/llvm/test/Transforms/LoopDeletion/pr53969.ll
index f9b9dc3373b5e..3b8904e4457f8 100644
--- a/llvm/test/Transforms/LoopDeletion/pr53969.ll
+++ b/llvm/test/Transforms/LoopDeletion/pr53969.ll
@@ -44,7 +44,7 @@ define void @test() {
 ; CHECK-NEXT:    br i1 false, label [[BB11]], label [[BB12:%.*]]
 ; CHECK:       bb42:
 ; CHECK-NEXT:    [[TMP24_LCSSA:%.*]] = phi i32 [ undef, [[BB22]] ]
-; CHECK-NEXT:    [[TMP18_LCSSA4:%.*]] = phi i64 [ 0, [[BB22]] ]
+; CHECK-NEXT:    [[TMP18_LCSSA4:%.*]] = phi i64 [ undef, [[BB22]] ]
 ; CHECK-NEXT:    store atomic i64 [[TMP18_LCSSA4]], ptr addrspace(1) undef unordered, align 8
 ; CHECK-NEXT:    call void @use(i32 [[TMP24_LCSSA]])
 ; CHECK-NEXT:    ret void
diff --git a/llvm/test/Transforms/LoopStrengthReduce/X86/2012-01-13-phielim.ll b/llvm/test/Transforms/LoopStrengthReduce/X86/2012-01-13-phielim.ll
index c4aa6c7725d41..b0b8234b18380 100644
--- a/llvm/test/Transforms/LoopStrengthReduce/X86/2012-01-13-phielim.ll
+++ b/llvm/test/Transforms/LoopStrengthReduce/X86/2012-01-13-phielim.ll
@@ -156,29 +156,29 @@ define fastcc void @test3(ptr nocapture %u) nounwind uwtable ssp {
 ; CHECK:       for.inc8.us.i:
 ; CHECK-NEXT:    br i1 true, label [[MESHBB1_LOOPEXIT:%.*]], label [[MESHBB:%.*]]
 ; CHECK:       for.body3.us.i:
-; CHECK-NEXT:    [[INDVARS_IV_I_SV_PHI:%.*]] = phi i64 [ [[INDVARS_IV_NEXT_I:%.*]], [[MESHBB]] ], [ 0, [[FOR_BODY3_LR_PH_US_I:%.*]] ]
+; CHECK-NEXT:    [[LSR_IV1:%.*]] = phi i32 [ [[LSR_IV_NEXT:%.*]], [[MESHBB]] ], [ [[TMP2:%.*]], [[FOR_BODY3_LR_PH_US_I:%.*]] ]
+; CHECK-NEXT:    [[LSR_IV:%.*]] = phi ptr [ [[SCEVGEP:%.*]], [[MESHBB]] ], [ [[U:%.*]], [[FOR_BODY3_LR_PH_US_I]] ]
 ; CHECK-NEXT:    [[OPQ_SA_CALC12:%.*]] = sub i32 undef, 227
-; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[LSR_IV:%.*]], [[INDVARS_IV_I_SV_PHI]]
-; CHECK-NEXT:    [[TMP:%.*]] = trunc i64 [[TMP0]] to i32
-; CHECK-NEXT:    [[MUL_I_US_I:%.*]] = mul nsw i32 0, [[TMP]]
-; CHECK-NEXT:    [[TMP1:%.*]] = shl nuw nsw i64 [[INDVARS_IV_I_SV_PHI]], 3
-; CHECK-NEXT:    [[SCEVGEP:%.*]] = getelementptr i8, ptr [[U:%.*]], i64 [[TMP1]]
-; CHECK-NEXT:    [[TMP2:%.*]] = load double, ptr [[SCEVGEP]], align 8
+; CHECK-NEXT:    [[MUL_I_US_I:%.*]] = mul nsw i32 0, [[LSR_IV1]]
+; CHECK-NEXT:    [[TMP0:%.*]] = load double, ptr [[LSR_IV]], align 8
 ; CHECK-NEXT:    br i1 undef, label [[FOR_INC8_US_I:%.*]], label [[MESHBB]]
 ; CHECK:       for.body3.lr.ph.us.i.loopexit:
-; CHECK-NEXT:    [[LSR_IV_NEXT:%.*]] = add i64 [[LSR_IV]], 1
 ; CHECK-NEXT:    br label [[FOR_BODY3_LR_PH_US_I]]
 ; CHECK:       for.body3.lr.ph.us.i:
-; CHECK-NEXT:    [[LSR_IV]] = phi i64 [ [[LSR_IV_NEXT]], [[FOR_BODY3_LR_PH_US_I_LOOPEXIT:%.*]] ], [ undef, [[MESHBB1]] ]
-; CHECK-NEXT:    [[ARRAYIDX_US_I:%.*]] = getelementptr inbounds double, ptr undef, i64 [[LSR_IV]]
+; CHECK-NEXT:    [[INDVARS_IV8_I_SV_PHI26:%.*]] = phi i64 [ poison, [[MESHBB1]] ], [ [[INDVARS_IV8_I_SV_PHI24:%.*]], [[FOR_BODY3_LR_PH_US_I_LOOPEXIT:%.*]] ]
+; CHECK-NEXT:    [[ARRAYIDX_US_I:%.*]] = getelementptr inbounds double, ptr undef, i64 [[INDVARS_IV8_I_SV_PHI26]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add i64 [[INDVARS_IV8_I_SV_PHI26]], 1
+; CHECK-NEXT:    [[TMP2]] = trunc i64 [[INDVARS_IV8_I_SV_PHI26]] to i32
 ; CHECK-NEXT:    br label [[FOR_BODY3_US_I:%.*]]
 ; CHECK:       for.inc8.us.i2:
 ; CHECK-NEXT:    unreachable
 ; CHECK:       eval_At_times_u.exit:
 ; CHECK-NEXT:    ret void
 ; CHECK:       meshBB:
+; CHECK-NEXT:    [[INDVARS_IV8_I_SV_PHI24]] = phi i64 [ undef, [[FOR_BODY3_US_I]] ], [ [[TMP1]], [[FOR_INC8_US_I]] ]
 ; CHECK-NEXT:    [[MESHSTACKVARIABLE_PHI:%.*]] = phi i32 [ [[OPQ_SA_CALC12]], [[FOR_BODY3_US_I]] ], [ undef, [[FOR_INC8_US_I]] ]
-; CHECK-NEXT:    [[INDVARS_IV_NEXT_I]] = add i64 [[INDVARS_IV_I_SV_PHI]], 1
+; CHECK-NEXT:    [[SCEVGEP]] = getelementptr i8, ptr [[LSR_IV]], i64 8
+; CHECK-NEXT:    [[LSR_IV_NEXT]] = add i32 [[LSR_IV1]], 1
 ; CHECK-NEXT:    br i1 true, label [[FOR_BODY3_LR_PH_US_I_LOOPEXIT]], label [[FOR_BODY3_US_I]]
 ; CHECK:       meshBB1.loopexit:
 ; CHECK-NEXT:    br label [[MESHBB1]]
@@ -206,7 +206,7 @@ for.body3.us.i:                                   ; preds = %meshBB, %for.body3.
   br i1 undef, label %for.inc8.us.i, label %meshBB
 
 for.body3.lr.ph.us.i:                             ; preds = %meshBB1, %meshBB
-  %indvars.iv8.i.SV.phi26 = phi i64 [ undef, %meshBB1 ], [ %indvars.iv8.i.SV.phi24, %meshBB ]
+  %indvars.iv8.i.SV.phi26 = phi i64 [ poison, %meshBB1 ], [ %indvars.iv8.i.SV.phi24, %meshBB ]
   %arrayidx.us.i = getelementptr inbounds double, ptr undef, i64 %indvars.iv8.i.SV.phi26
   %3 = add i64 %indvars.iv8.i.SV.phi26, 1
   br label %for.body3.us.i
diff --git a/llvm/test/Transforms/LoopVectorize/pr31190.ll b/llvm/test/Transforms/LoopVectorize/pr31190.ll
index b6cacf1a7fe87..c4f1f9c5d8f0c 100644
--- a/llvm/test/Transforms/LoopVectorize/pr31190.ll
+++ b/llvm/test/Transforms/LoopVectorize/pr31190.ll
@@ -5,7 +5,7 @@
 ; is a SCEV AddRec with respect to an outer loop.
 
 ; In this case, the problematic PHI is:
-; %0 = phi i32 [ undef, %for.cond1.preheader ], [ %inc54, %for.body3 ]
+; %0 = phi i32 [ poison, %for.cond1.preheader ], [ %inc54, %for.body3 ]
 ; Since %inc54 is the IV of the outer loop, and %0 equivalent to it,
 ; we get the situation described above.
 
@@ -47,7 +47,7 @@ for.cond1.preheader:                              ; preds = %for.cond1.for.inc4_
 
 for.body3:                                        ; preds = %for.body3, %for.cond1.preheader
   %inc1 = phi i32 [ %inc.lcssa3, %for.cond1.preheader ], [ %inc, %for.body3 ]
-  %0 = phi i32 [ undef, %for.cond1.preheader ], [ %inc54, %for.body3 ]
+  %0 = phi i32 [ poison, %for.cond1.preheader ], [ %inc54, %for.body3 ]
   %idxprom = sext i32 %0 to i64
   %arrayidx = getelementptr inbounds [1 x i32], ptr @b, i64 0, i64 %idxprom
   store i32 4, ptr %arrayidx, align 4
diff --git a/llvm/test/Transforms/LoopVectorize/uniform-blend.ll b/llvm/test/Transforms/LoopVectorize/uniform-blend.ll
index c9fc8beb006d9..ecc1ae817b687 100644
--- a/llvm/test/Transforms/LoopVectorize/uniform-blend.ll
+++ b/llvm/test/Transforms/LoopVectorize/uniform-blend.ll
@@ -14,9 +14,9 @@ define void @blend_uniform_iv_trunc(i1 %c) {
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, %[[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], %[[VECTOR_BODY]] ]
 ; CHECK-NEXT:    [[TMP0:%.*]] = trunc i64 [[INDEX]] to i16
 ; CHECK-NEXT:    [[TMP1:%.*]] = add i16 [[TMP0]], 0
-; CHECK-NEXT:    [[PREDPHI:%.*]] = select i1 [[C]], i16 [[TMP1]], i16 undef
-; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr inbounds [32 x i16], ptr @dst, i16 0, i16 [[PREDPHI]]
-; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr inbounds i16, ptr [[TMP2]], i32 0
+; CHECK-NEXT:    [[TMP6:%.*]] = select i1 [[C]], i16 [[TMP1]], i16 poison
+; CHECK-NEXT:    [[TMP7:%.*]] = getelementptr inbounds [32 x i16], ptr @dst, i16 0, i16 [[TMP6]]
+; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr inbounds i16, ptr [[TMP7]], i32 0
 ; CHE...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/96631


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