http://llvm.org/bugs/show_bug.cgi?id=2599
Summary: Missed DSE case
Product: libraries
Version: 1.0
Platform: PC
OS/Version: All
Status: NEW
Keywords: code-quality
Severity: normal
Priority: P2
Component: Scalar Optimizations
AssignedTo: [EMAIL PROTECTED]
ReportedBy: [EMAIL PROTECTED]
CC: [email protected]
DSE should delete a store to a location when the stored value is the same as
the loaded one. For example:
void foo(_Complex int *x) {
*x = ~*x;
}
compiles to:
define void @foo({ i32, i32 }* %x) nounwind {
entry:
getelementptr { i32, i32 }* %x, i32 0, i32 0 ; <i32*>:0
[#uses=2]
load i32* %0, align 4 ; <i32>:1 [#uses=1]
getelementptr { i32, i32 }* %x, i32 0, i32 1 ; <i32*>:2
[#uses=2]
load i32* %2, align 4 ; <i32>:3 [#uses=1]
sub i32 0, %3 ; <i32>:4 [#uses=1]
store i32 %1, i32* %0, align 4
store i32 %4, i32* %2, align 4
ret void
}
The load+store to %0 should be nuked, which would happen if DSE deleted the
store to %0.
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