[PATCH] D59211: [LSR] Check for signed overflow in NarrowSearchSpaceByDetectingSupersets.

[Florian Hahn via Phabricator via llvm-commits]

fhahn updated this revision to Diff 190142.
fhahn added a comment.

use wrapping arithmetic


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D59211/new/

https://reviews.llvm.org/D59211

Files:
  llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
  llvm/test/Transforms/LoopStrengthReduce/X86/lsr-overflow.ll


Index: llvm/test/Transforms/LoopStrengthReduce/X86/lsr-overflow.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopStrengthReduce/X86/lsr-overflow.ll
@@ -0,0 +1,38 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -lsr-complexity-limit=50 -loop-reduce -S %s | FileCheck %s
+
+target triple = "x86_64-apple-macosx10.14.0"
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+define void @overflow1(i64 %a) {
+; CHECK-LABEL: @overflow1(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br label [[BB1:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[TMP:%.*]] = phi i64 [ [[A:%.*]], [[BB:%.*]] ], [ [[TMP6:%.*]], [[BB1]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[TMP]], -9223372036854775808
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp ne i64 [[TMP0]], 0
+; CHECK-NEXT:    [[TMP5:%.*]] = and i1 [[TMP4]], true
+; CHECK-NEXT:    [[TMP6]] = add i64 [[TMP]], 1
+; CHECK-NEXT:    br i1 [[TMP5]], label [[BB1]], label [[BB7:%.*]]
+; CHECK:       bb7:
+; CHECK-NEXT:    [[TMP1:%.*]] = add i64 [[TMP6]], -1
+; CHECK-NEXT:    [[TMP9:%.*]] = and i64 [[TMP1]], 1
+; CHECK-NEXT:    [[TMP10:%.*]] = icmp eq i64 [[TMP9]], 0
+; CHECK-NEXT:    unreachable
+;
+bb:
+  br label %bb1
+
+bb1:                                              ; preds = %bb1, %bb
+  %tmp = phi i64 [ %a, %bb ], [ %tmp6, %bb1 ]
+  %tmp4 = icmp ne i64 %tmp, -9223372036854775808
+  %tmp5 = and i1 %tmp4, 1
+  %tmp6 = add i64 %tmp, 1
+  br i1 %tmp5, label %bb1, label %bb7
+
+bb7:                                              ; preds = %bb1
+  %tmp9 = and i64 %tmp, 1
+  %tmp10 = icmp eq i64 %tmp9, 0
+  unreachable
+}
Index: llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -4435,7 +4435,9 @@
              I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
           if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
             Formula NewF = F;
-            NewF.BaseOffset += C->getValue()->getSExtValue();
+            //FIXME: Formulas should store bitwidth to do wrapping properly.
+            //       See PR41034.
+            NewF.BaseOffset += (uint64_t)C->getValue()->getSExtValue();
             NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
                                 (I - F.BaseRegs.begin()));
             if (LU.HasFormulaWithSameRegs(NewF)) {


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