<div dir="ltr">Hi Hans,<div><br></div><div>[cc. Richard as code owner]</div><div><br></div><div>I'd like to nominate this commit for 3.9. The actual code churn is tiny, and this fixes a problem noticed by and causing pain to the qemu project.</div><div><br></div><div>Cheers,</div><div><br></div><div>James<br><br><div class="gmail_quote"><div dir="ltr">On Tue, 16 Aug 2016 at 10:53 James Molloy via cfe-commits <<a href="mailto:cfe-commits@lists.llvm.org">cfe-commits@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: jamesm<br>
Date: Tue Aug 16 04:45:36 2016<br>
New Revision: 278786<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=278786&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=278786&view=rev</a><br>
Log:<br>
Left shifts of negative values are defined if -fwrapv is set<br>
<br>
This means we shouldn't emit ubsan detection code or warn.<br>
Fixes PR25552.<br>
<br>
Added:<br>
cfe/trunk/test/CodeGen/wrapv-lshr-sanitize.c<br>
cfe/trunk/test/Sema/negative-shift-wrapv.c<br>
Modified:<br>
cfe/trunk/lib/CodeGen/CGExprScalar.cpp<br>
cfe/trunk/lib/Sema/SemaExpr.cpp<br>
<br>
Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprScalar.cpp?rev=278786&r1=278785&r2=278786&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprScalar.cpp?rev=278786&r1=278785&r2=278786&view=diff</a><br>
==============================================================================<br>
--- cfe/trunk/lib/CodeGen/CGExprScalar.cpp (original)<br>
+++ cfe/trunk/lib/CodeGen/CGExprScalar.cpp Tue Aug 16 04:45:36 2016<br>
@@ -2714,7 +2714,8 @@ Value *ScalarExprEmitter::EmitShl(const<br>
RHS = Builder.CreateIntCast(RHS, Ops.LHS->getType(), false, "sh_prom");<br>
<br>
bool SanitizeBase = CGF.SanOpts.has(SanitizerKind::ShiftBase) &&<br>
- Ops.Ty->hasSignedIntegerRepresentation();<br>
+ Ops.Ty->hasSignedIntegerRepresentation() &&<br>
+ !CGF.getLangOpts().isSignedOverflowDefined();<br>
bool SanitizeExponent = CGF.SanOpts.has(SanitizerKind::ShiftExponent);<br>
// OpenCL 6.3j: shift values are effectively % word size of LHS.<br>
if (CGF.getLangOpts().OpenCL)<br>
<br>
Modified: cfe/trunk/lib/Sema/SemaExpr.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=278786&r1=278785&r2=278786&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=278786&r1=278785&r2=278786&view=diff</a><br>
==============================================================================<br>
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)<br>
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Tue Aug 16 04:45:36 2016<br>
@@ -8670,7 +8670,7 @@ static void DiagnoseBadShiftValues(Sema&<br>
<br>
// If LHS does not have a signed type and non-negative value<br>
// then, the behavior is undefined. Warn about it.<br>
- if (Left.isNegative()) {<br>
+ if (Left.isNegative() && !S.getLangOpts().isSignedOverflowDefined()) {<br>
S.DiagRuntimeBehavior(Loc, LHS.get(),<br>
S.PDiag(diag::warn_shift_lhs_negative)<br>
<< LHS.get()->getSourceRange());<br>
<br>
Added: cfe/trunk/test/CodeGen/wrapv-lshr-sanitize.c<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/wrapv-lshr-sanitize.c?rev=278786&view=auto" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/wrapv-lshr-sanitize.c?rev=278786&view=auto</a><br>
==============================================================================<br>
--- cfe/trunk/test/CodeGen/wrapv-lshr-sanitize.c (added)<br>
+++ cfe/trunk/test/CodeGen/wrapv-lshr-sanitize.c Tue Aug 16 04:45:36 2016<br>
@@ -0,0 +1,12 @@<br>
+// RUN: %clang_cc1 -fsanitize=shift-base -emit-llvm %s -o - -triple x86_64-linux-gnu -fwrapv | FileCheck %s<br>
+<br>
+// CHECK-LABEL: @lsh_overflow<br>
+int lsh_overflow(int a, int b) {<br>
+ // CHECK-NOT: br<br>
+ // CHECK-NOT: call void @__ubsan_<br>
+ // CHECK-NOT: call void @llvm.trap<br>
+<br>
+ // CHECK: %[[RET:.*]] = shl i32<br>
+ // CHECK-NEXT: ret i32 %[[RET]]<br>
+ return a << b;<br>
+}<br>
<br>
Added: cfe/trunk/test/Sema/negative-shift-wrapv.c<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/negative-shift-wrapv.c?rev=278786&view=auto" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/negative-shift-wrapv.c?rev=278786&view=auto</a><br>
==============================================================================<br>
--- cfe/trunk/test/Sema/negative-shift-wrapv.c (added)<br>
+++ cfe/trunk/test/Sema/negative-shift-wrapv.c Tue Aug 16 04:45:36 2016<br>
@@ -0,0 +1,9 @@<br>
+// RUN: %clang_cc1 -Wall -ffreestanding -fsyntax-only -fwrapv -verify %s<br>
+<br>
+int test() {<br>
+ int i;<br>
+ i = -1 << 1; // no-warning<br>
+ return i;<br>
+}<br>
+<br>
+// expected-no-diagnostics<br>
<br>
<br>
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</blockquote></div></div></div>