[PATCH] D126546: [InstCombine] decomposeSimpleLinearExpr should bail out on negative operands.
wael yehia via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 7 17:58:24 PDT 2022
This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG0952cf5bbbc4: [InstCombine] decomposeSimpleLinearExpr should bail out on negative operands. (authored by w2yehia).
Changed prior to commit:
https://reviews.llvm.org/D126546?vs=434866&id=435009#toc
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D126546/new/
https://reviews.llvm.org/D126546
Files:
llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
llvm/test/Transforms/InstCombine/2011-06-13-nsw-alloca.ll
llvm/test/Transforms/InstCombine/neg-alloca.ll
Index: llvm/test/Transforms/InstCombine/neg-alloca.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/InstCombine/neg-alloca.ll
@@ -0,0 +1,21 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+declare void @use(i32 *)
+
+define void @foo(i64 %X) {
+; Currently we cannot handle expressions of the form Offset - X * Scale.
+; CHECK-LABEL: @foo(
+; CHECK-NEXT: [[TMP1:%.*]] = mul nsw i64 [[X:%.*]], -4
+; CHECK-NEXT: [[TMP2:%.*]] = add nsw i64 [[TMP1]], 24
+; CHECK-NEXT: [[TMP3:%.*]] = alloca i8, i64 [[TMP2]], align 4
+; CHECK-NEXT: [[TMP4:%.*]] = bitcast i8* [[TMP3]] to i32*
+; CHECK-NEXT: call void @use(i32* nonnull [[TMP4]])
+; CHECK-NEXT: ret void
+;
+ %1 = mul nsw i64 %X, -4
+ %2 = add nsw i64 %1, 24
+ %3 = alloca i8, i64 %2, align 4
+ %4 = bitcast i8* %3 to i32*
+ call void @use(i32 *%4)
+ ret void
+}
Index: llvm/test/Transforms/InstCombine/2011-06-13-nsw-alloca.ll
===================================================================
--- llvm/test/Transforms/InstCombine/2011-06-13-nsw-alloca.ll
+++ llvm/test/Transforms/InstCombine/2011-06-13-nsw-alloca.ll
@@ -15,9 +15,9 @@
; <label>:4 ; preds = %0
%5 = load i32, i32* %1, align 4
- %6 = shl nsw i32 %5, 3
-; With "nsw", the alloca and its bitcast can be fused:
- %7 = add nsw i32 %6, 2048
+ %6 = shl nuw i32 %5, 3
+; With "nuw", the alloca and its bitcast can be fused:
+ %7 = add nuw i32 %6, 2048
; CHECK: alloca double
%8 = alloca i8, i32 %7
%9 = bitcast i8* %8 to double*
@@ -45,8 +45,8 @@
; <label>:4 ; preds = %0
%5 = load i32, i32* %1, align 4
- %6 = mul nsw i32 %5, 8
-; Without "nsw", the alloca and its bitcast cannot be fused:
+ %6 = mul nuw i32 %5, 8
+; Without "nuw", the alloca and its bitcast cannot be fused:
%7 = add i32 %6, 2048
; CHECK: alloca i8
%8 = alloca i8, i32 %7
Index: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -36,8 +36,10 @@
if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
// Cannot look past anything that might overflow.
+ // We specifically require nuw because we store the Scale in an unsigned
+ // and perform an unsigned divide on it.
OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val);
- if (OBI && !OBI->hasNoUnsignedWrap() && !OBI->hasNoSignedWrap()) {
+ if (OBI && !OBI->hasNoUnsignedWrap()) {
Scale = 1;
Offset = 0;
return Val;
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