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MemoryDependenceAnalysis attempts to find the first memory dependency for function calls.

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Currently, if GetLocation reports that it did not find a valid pointer (this is the case for volatile load/stores),
we ignore the result. This patch adds code to handle the cases where we did not obtain a valid pointer.

rdar://11872864  PR12899



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161802 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem 2012-08-13 23:03:43 +00:00
parent 6d2986cd03
commit 8dff60e96a
2 changed files with 41 additions and 2 deletions
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9
lib/Analysis/MemoryDependenceAnalysis.cpp
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@ -227,13 +227,18 @@ getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
// Otherwise if the two calls don't interact (e.g. InstCS is readnone)
// keep scanning.
break;
continue;
default:
return MemDepResult::getClobber(Inst);
}
}
// If we could not obtain a pointer for the instruction and the instruction
// touches memory then assume that this is a dependency.
if (MR != AliasAnalysis::NoModRef)
return MemDepResult::getClobber(Inst);
}
// No dependence found. If this is the entry block of the function, it is
// unknown, otherwise it is non-local.
if (BB != &BB->getParent()->getEntryBlock())

34
test/Analysis/GlobalsModRef/volatile-instrs.ll Normal file
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@ -0,0 +1,34 @@
; RUN: opt < %s -basicaa -dse -S | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.8.0"
%struct.anon = type { i32, i32, i32 }
@b = global %struct.anon { i32 1, i32 0, i32 0 }, align 4
@c = common global i32 0, align 4
@a = common global %struct.anon zeroinitializer, align 4
@.str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
declare i32 @printf(i8* nocapture, ...) nounwind
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
; Make sure that the initial memcpy call does not go away
; because the volatile load is in the way. PR12899
; CHECK: main_entry:
; CHECK-NEXT: tail call void @llvm.memcpy.p0i8.p0i8.i64
define i32 @main() nounwind uwtable ssp {
main_entry:
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* bitcast (%struct.anon* @b to i8*), i8* bitcast (%struct.anon* @a to i8*), i64 12, i32 4, i1 false)
%0 = load volatile i32* getelementptr inbounds (%struct.anon* @b, i64 0, i32 0), align 4, !tbaa !0
store i32 %0, i32* @c, align 4, !tbaa !0
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* bitcast (%struct.anon* @b to i8*), i8* bitcast (%struct.anon* @a to i8*), i64 12, i32 4, i1 false) nounwind
%call = tail call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([4 x i8]* @.str, i64 0, i64 0), i32 %0) nounwind
ret i32 0
}
!0 = metadata !{metadata !"int", metadata !1}
!1 = metadata !{metadata !"omnipotent char", metadata !2}
!2 = metadata !{metadata !"Simple C/C++ TBAA"}