[PATCH] D127736: [Matrix] Check if iterator is at beginning of BB in optimizeTranspose.

Florian Hahn via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Tue Jun 14 03:40:06 PDT 2022 

fhahn created this revision.
fhahn added reviewers: anemet, thegameg.
Herald added subscribers: tschuett, hiraditya.
Herald added a project: All.
fhahn requested review of this revision.
Herald added a project: LLVM.

If an instruction at the beginning of a block is erased,  this may
trigger crash due to dereferencing an invalid iterator.

Check if II is at the end before dereferencing it.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D127736

Files:
  llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
  llvm/test/Transforms/LowerMatrixIntrinsics/transpose-opts-iterator-invalidation.ll


Index: llvm/test/Transforms/LowerMatrixIntrinsics/transpose-opts-iterator-invalidation.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LowerMatrixIntrinsics/transpose-opts-iterator-invalidation.ll
@@ -0,0 +1,61 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=lower-matrix-intrinsics -S %s | FileCheck %s
+
+define <2 x double> @test(<4 x double> %a, <2 x double> %b, i1 %c) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[EXIT_1:%.*]], label [[EXIT_2:%.*]]
+; CHECK:       exit.1:
+; CHECK-NEXT:    [[SPLIT:%.*]] = shufflevector <4 x double> [[A:%.*]], <4 x double> poison, <2 x i32> <i32 0, i32 1>
+; CHECK-NEXT:    [[SPLIT1:%.*]] = shufflevector <4 x double> [[A]], <4 x double> poison, <2 x i32> <i32 2, i32 3>
+; CHECK-NEXT:    [[SPLIT2:%.*]] = shufflevector <2 x double> [[B:%.*]], <2 x double> poison, <2 x i32> <i32 0, i32 1>
+; CHECK-NEXT:    [[BLOCK:%.*]] = shufflevector <2 x double> [[SPLIT]], <2 x double> poison, <1 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP0:%.*]] = extractelement <2 x double> [[SPLIT2]], i64 0
+; CHECK-NEXT:    [[SPLAT_SPLATINSERT:%.*]] = insertelement <1 x double> poison, double [[TMP0]], i32 0
+; CHECK-NEXT:    [[SPLAT_SPLAT:%.*]] = shufflevector <1 x double> [[SPLAT_SPLATINSERT]], <1 x double> poison, <1 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul <1 x double> [[BLOCK]], [[SPLAT_SPLAT]]
+; CHECK-NEXT:    [[BLOCK3:%.*]] = shufflevector <2 x double> [[SPLIT1]], <2 x double> poison, <1 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP2:%.*]] = extractelement <2 x double> [[SPLIT2]], i64 1
+; CHECK-NEXT:    [[SPLAT_SPLATINSERT4:%.*]] = insertelement <1 x double> poison, double [[TMP2]], i32 0
+; CHECK-NEXT:    [[SPLAT_SPLAT5:%.*]] = shufflevector <1 x double> [[SPLAT_SPLATINSERT4]], <1 x double> poison, <1 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP3:%.*]] = fmul <1 x double> [[BLOCK3]], [[SPLAT_SPLAT5]]
+; CHECK-NEXT:    [[TMP4:%.*]] = fadd <1 x double> [[TMP1]], [[TMP3]]
+; CHECK-NEXT:    [[TMP5:%.*]] = shufflevector <1 x double> [[TMP4]], <1 x double> poison, <2 x i32> <i32 0, i32 undef>
+; CHECK-NEXT:    [[TMP6:%.*]] = shufflevector <2 x double> undef, <2 x double> [[TMP5]], <2 x i32> <i32 2, i32 1>
+; CHECK-NEXT:    [[BLOCK6:%.*]] = shufflevector <2 x double> [[SPLIT]], <2 x double> poison, <1 x i32> <i32 1>
+; CHECK-NEXT:    [[TMP7:%.*]] = extractelement <2 x double> [[SPLIT2]], i64 0
+; CHECK-NEXT:    [[SPLAT_SPLATINSERT7:%.*]] = insertelement <1 x double> poison, double [[TMP7]], i32 0
+; CHECK-NEXT:    [[SPLAT_SPLAT8:%.*]] = shufflevector <1 x double> [[SPLAT_SPLATINSERT7]], <1 x double> poison, <1 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP8:%.*]] = fmul <1 x double> [[BLOCK6]], [[SPLAT_SPLAT8]]
+; CHECK-NEXT:    [[BLOCK9:%.*]] = shufflevector <2 x double> [[SPLIT1]], <2 x double> poison, <1 x i32> <i32 1>
+; CHECK-NEXT:    [[TMP9:%.*]] = extractelement <2 x double> [[SPLIT2]], i64 1
+; CHECK-NEXT:    [[SPLAT_SPLATINSERT10:%.*]] = insertelement <1 x double> poison, double [[TMP9]], i32 0
+; CHECK-NEXT:    [[SPLAT_SPLAT11:%.*]] = shufflevector <1 x double> [[SPLAT_SPLATINSERT10]], <1 x double> poison, <1 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP10:%.*]] = fmul <1 x double> [[BLOCK9]], [[SPLAT_SPLAT11]]
+; CHECK-NEXT:    [[TMP11:%.*]] = fadd <1 x double> [[TMP8]], [[TMP10]]
+; CHECK-NEXT:    [[TMP12:%.*]] = shufflevector <1 x double> [[TMP11]], <1 x double> poison, <2 x i32> <i32 0, i32 undef>
+; CHECK-NEXT:    [[TMP13:%.*]] = shufflevector <2 x double> [[TMP6]], <2 x double> [[TMP12]], <2 x i32> <i32 0, i32 2>
+; CHECK-NEXT:    [[TMP14:%.*]] = extractelement <2 x double> [[TMP13]], i64 0
+; CHECK-NEXT:    [[TMP15:%.*]] = insertelement <1 x double> undef, double [[TMP14]], i64 0
+; CHECK-NEXT:    [[TMP16:%.*]] = extractelement <2 x double> [[TMP13]], i64 1
+; CHECK-NEXT:    [[TMP17:%.*]] = insertelement <1 x double> undef, double [[TMP16]], i64 0
+; CHECK-NEXT:    [[TMP18:%.*]] = shufflevector <1 x double> [[TMP15]], <1 x double> [[TMP17]], <2 x i32> <i32 0, i32 1>
+; CHECK-NEXT:    ret <2 x double> [[TMP18]]
+; CHECK:       exit.2:
+; CHECK-NEXT:    ret <2 x double> zeroinitializer
+;
+entry:
+  %mult = call <2 x double> @llvm.matrix.multiply.v2f64.v4f64.v2f64(<4 x double> %a, <2 x double> %b, i32 2, i32 2, i32 1)
+  br i1 %c, label %exit.1, label %exit.2
+
+exit.1:
+  %trans = call <2 x double> @llvm.matrix.transpose.v2f64(<2 x double> %mult, i32 2, i32 1)
+  ret <2 x double> %trans
+
+exit.2:
+  ret <2 x double> zeroinitializer
+}
+
+declare <2 x double> @llvm.matrix.transpose.v2f64(<2 x double>, i32 immarg, i32 immarg)
+
+declare <2 x double> @llvm.matrix.multiply.v2f64.v4f64.v2f64(<4 x double>, <2 x double>, i32 immarg, i32 immarg, i32 immarg)
Index: llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
+++ llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
@@ -704,10 +704,10 @@
         // We may remove II.  By default continue on the next/prev instruction.
         ++II;
         // If we were to erase II, move again.
-        auto EraseFromParent = [&II](Value *V) {
+        auto EraseFromParent = [&II, &BB](Value *V) {
           auto *Inst = cast<Instruction>(V);
           if (Inst->use_empty()) {
-            if (Inst == &*II) {
+            if (II != BB.rend() && Inst == &*II) {
               ++II;
             }
             Inst->eraseFromParent();


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