Author: Nikita Popov Date: 2021-01-17T20:06:17+01:00 New Revision: 4229b87ed36cf20b95b363393452aa4815e344e2
URL: https://github.com/llvm/llvm-project/commit/4229b87ed36cf20b95b363393452aa4815e344e2 DIFF: https://github.com/llvm/llvm-project/commit/4229b87ed36cf20b95b363393452aa4815e344e2.diff LOG: [ValueTracking] Fix isSafeToSpeculativelyExecute for sdiv (PR48778) The != -1 check does not work correctly for all bitwidths. Use isAllOnesValue() instead. Added: Modified: llvm/lib/Analysis/ValueTracking.cpp llvm/test/Transforms/SimplifyCFG/pr48778-sdiv-speculation.ll Removed: ################################################################################ diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 61c992d0eedf..a9cef91e7316 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -4391,7 +4391,7 @@ bool llvm::isSafeToSpeculativelyExecute(const Value *V, if (*Denominator == 0) return false; // It's safe to hoist if the denominator is not 0 or -1. - if (*Denominator != -1) + if (!Denominator->isAllOnesValue()) return true; // At this point we know that the denominator is -1. It is safe to hoist as // long we know that the numerator is not INT_MIN. diff --git a/llvm/test/Transforms/SimplifyCFG/pr48778-sdiv-speculation.ll b/llvm/test/Transforms/SimplifyCFG/pr48778-sdiv-speculation.ll index 992736c48572..cc59ea04c64e 100644 --- a/llvm/test/Transforms/SimplifyCFG/pr48778-sdiv-speculation.ll +++ b/llvm/test/Transforms/SimplifyCFG/pr48778-sdiv-speculation.ll @@ -4,11 +4,14 @@ ; sdiv INT_MIN / -1 should not be speculated. define i32 @test(i1 %cmp) { ; CHECK-LABEL: @test( -; CHECK-NEXT: else: +; CHECK-NEXT: br i1 [[CMP:%.*]], label [[IF:%.*]], label [[ELSE:%.*]] +; CHECK: if: ; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 -2147483648, -1 ; CHECK-NEXT: [[CMP2:%.*]] = icmp ne i32 [[DIV]], 0 -; CHECK-NEXT: [[OR_COND:%.*]] = and i1 [[CMP:%.*]], [[CMP2]] -; CHECK-NEXT: [[MERGE:%.*]] = select i1 [[OR_COND]], i32 1, i32 0 +; CHECK-NEXT: [[SPEC_SELECT:%.*]] = select i1 [[CMP2]], i32 1, i32 0 +; CHECK-NEXT: br label [[ELSE]] +; CHECK: else: +; CHECK-NEXT: [[MERGE:%.*]] = phi i32 [ 0, [[TMP0:%.*]] ], [ [[SPEC_SELECT]], [[IF]] ] ; CHECK-NEXT: ret i32 [[MERGE]] ; br i1 %cmp, label %if, label %else _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
