From d37a31cf237cb4f8a18b12c91a9204feca5900ef Mon Sep 17 00:00:00 2001 From: Craig Topper Date: Fri, 10 Feb 2023 10:02:51 -0800 Subject: [PATCH] [X86] Attempt to fix ubsan failure. operator~ promote the single bit input to int. The ~ will cause the upper 31 bits to become 1s making it a negative value. This is undefined for shift. Mask it back down to a single bit. The extra 1s were being shifted to bit 8 and above and the they aren't used by the emitByte call so this shouldn't be a functional change. --- llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp index 84b11af..cbdcba1 100644 --- a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp +++ b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp @@ -219,7 +219,7 @@ public: return; case VEX2: emitByte(0xC5, OS); - emitByte(~R << 7 | LastPayload, OS); + emitByte(((~R) & 1) << 7 | LastPayload, OS); return; case VEX3: case XOP: -- 2.7.4