https://github.com/nikic created https://github.com/llvm/llvm-project/pull/172301
Use getSigned() to create the 1 or -1 constant, so it gets properly sign extended. This miscompile was found while working on https://github.com/llvm/llvm-project/pull/171456. >From f9c0de4fa0959f432ae90d44a07c806eba028b45 Mon Sep 17 00:00:00 2001 From: Nikita Popov <[email protected]> Date: Mon, 15 Dec 2025 14:38:52 +0100 Subject: [PATCH] [CGExprScalar] Fix inc/dec of vector larger than 64-bit Use getSigned() to create the 1 or -1 constant, so it gets properly sign extended. --- clang/lib/CodeGen/CGExprScalar.cpp | 2 +- clang/test/CodeGen/SystemZ/zvector.c | 8 ++++---- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp index 769bc37b0e131..9b6497fca829a 100644 --- a/clang/lib/CodeGen/CGExprScalar.cpp +++ b/clang/lib/CodeGen/CGExprScalar.cpp @@ -3335,7 +3335,7 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV, // Vector increment/decrement. } else if (type->isVectorType()) { if (type->hasIntegerRepresentation()) { - llvm::Value *amt = llvm::ConstantInt::get(value->getType(), amount); + llvm::Value *amt = llvm::ConstantInt::getSigned(value->getType(), amount); value = Builder.CreateAdd(value, amt, isInc ? "inc" : "dec"); } else { diff --git a/clang/test/CodeGen/SystemZ/zvector.c b/clang/test/CodeGen/SystemZ/zvector.c index a0b654d9acc9a..35bee8d41df61 100644 --- a/clang/test/CodeGen/SystemZ/zvector.c +++ b/clang/test/CodeGen/SystemZ/zvector.c @@ -298,10 +298,10 @@ void test_postinc(void) { // CHECK-NEXT: [[DEC7:%.*]] = add <2 x i64> [[TMP7]], splat (i64 -1) // CHECK-NEXT: store volatile <2 x i64> [[DEC7]], ptr @ul2, align 8 // CHECK-NEXT: [[TMP8:%.*]] = load volatile <1 x i128>, ptr @slll2, align 8 -// CHECK-NEXT: [[DEC8:%.*]] = add <1 x i128> [[TMP8]], splat (i128 18446744073709551615) +// CHECK-NEXT: [[DEC8:%.*]] = add <1 x i128> [[TMP8]], splat (i128 -1) // CHECK-NEXT: store volatile <1 x i128> [[DEC8]], ptr @slll2, align 8 // CHECK-NEXT: [[TMP9:%.*]] = load volatile <1 x i128>, ptr @ulll2, align 8 -// CHECK-NEXT: [[DEC9:%.*]] = add <1 x i128> [[TMP9]], splat (i128 18446744073709551615) +// CHECK-NEXT: [[DEC9:%.*]] = add <1 x i128> [[TMP9]], splat (i128 -1) // CHECK-NEXT: store volatile <1 x i128> [[DEC9]], ptr @ulll2, align 8 // CHECK-NEXT: [[TMP10:%.*]] = load volatile <2 x double>, ptr @fd2, align 8 // CHECK-NEXT: [[DEC10:%.*]] = fadd <2 x double> [[TMP10]], splat (double -1.000000e+00) @@ -356,10 +356,10 @@ void test_predec(void) { // CHECK-NEXT: [[DEC7:%.*]] = add <2 x i64> [[TMP7]], splat (i64 -1) // CHECK-NEXT: store volatile <2 x i64> [[DEC7]], ptr @ul2, align 8 // CHECK-NEXT: [[TMP8:%.*]] = load volatile <1 x i128>, ptr @slll2, align 8 -// CHECK-NEXT: [[DEC8:%.*]] = add <1 x i128> [[TMP8]], splat (i128 18446744073709551615) +// CHECK-NEXT: [[DEC8:%.*]] = add <1 x i128> [[TMP8]], splat (i128 -1) // CHECK-NEXT: store volatile <1 x i128> [[DEC8]], ptr @slll2, align 8 // CHECK-NEXT: [[TMP9:%.*]] = load volatile <1 x i128>, ptr @ulll2, align 8 -// CHECK-NEXT: [[DEC9:%.*]] = add <1 x i128> [[TMP9]], splat (i128 18446744073709551615) +// CHECK-NEXT: [[DEC9:%.*]] = add <1 x i128> [[TMP9]], splat (i128 -1) // CHECK-NEXT: store volatile <1 x i128> [[DEC9]], ptr @ulll2, align 8 // CHECK-NEXT: [[TMP10:%.*]] = load volatile <2 x double>, ptr @fd2, align 8 // CHECK-NEXT: [[DEC10:%.*]] = fadd <2 x double> [[TMP10]], splat (double -1.000000e+00) _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
