[PATCH] D23498: Left shifts of negative values are defined if -fwrapv is set
James Molloy via cfe-commits
cfe-commits at lists.llvm.org
Mon Aug 15 06:55:23 PDT 2016
jmolloy updated this revision to Diff 68033.
jmolloy added a comment.
Hi Filipe,
Thanks for the review! SGTM on both counts.
https://reviews.llvm.org/D23498
Files:
lib/CodeGen/CGExprScalar.cpp
lib/Sema/SemaExpr.cpp
test/CodeGen/wrapv-lshr-sanitize.c
test/Sema/negative-shift-wrapv.c
Index: test/Sema/negative-shift-wrapv.c
===================================================================
--- /dev/null
+++ test/Sema/negative-shift-wrapv.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -Wall -ffreestanding -fsyntax-only -fwrapv -verify %s
+
+int test() {
+ int i;
+ i = -1 << 1; // no-warning
+ return i;
+}
+
+// expected-no-diagnostics
Index: test/CodeGen/wrapv-lshr-sanitize.c
===================================================================
--- /dev/null
+++ test/CodeGen/wrapv-lshr-sanitize.c
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -fsanitize=shift-base -emit-llvm %s -o - -triple x86_64-linux-gnu -fwrapv | FileCheck %s
+
+// CHECK-LABEL: @lsh_overflow
+int lsh_overflow(int a, int b) {
+ // CHECK-NOT: br
+ // CHECK-NOT: call void @__ubsan_
+ // CHECK-NOT: call void @llvm.trap
+
+ // CHECK: %[[RET:.*]] = shl i32
+ // CHECK-NEXT: ret i32 %[[RET]]
+ return a << b;
+}
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -8567,7 +8567,7 @@
// If LHS does not have a signed type and non-negative value
// then, the behavior is undefined. Warn about it.
- if (Left.isNegative()) {
+ if (Left.isNegative() && !S.getLangOpts().isSignedOverflowDefined()) {
S.DiagRuntimeBehavior(Loc, LHS.get(),
S.PDiag(diag::warn_shift_lhs_negative)
<< LHS.get()->getSourceRange());
Index: lib/CodeGen/CGExprScalar.cpp
===================================================================
--- lib/CodeGen/CGExprScalar.cpp
+++ lib/CodeGen/CGExprScalar.cpp
@@ -2706,7 +2706,8 @@
RHS = Builder.CreateIntCast(RHS, Ops.LHS->getType(), false, "sh_prom");
bool SanitizeBase = CGF.SanOpts.has(SanitizerKind::ShiftBase) &&
- Ops.Ty->hasSignedIntegerRepresentation();
+ Ops.Ty->hasSignedIntegerRepresentation() &&
+ !CGF.getLangOpts().isSignedOverflowDefined();
bool SanitizeExponent = CGF.SanOpts.has(SanitizerKind::ShiftExponent);
// OpenCL 6.3j: shift values are effectively % word size of LHS.
if (CGF.getLangOpts().OpenCL)
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