http://llvm.org/bugs/show_bug.cgi?id=5816
Summary: Scalarrepl leads to nasty results with function
equivalent to fixed-size memmove
Product: new-bugs
Version: unspecified
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P2
Component: new bugs
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected], [email protected]
C Testcase:
#include <string.h>
void a(char* a, char* b) { char c[100]; memcpy(c, a, sizeof(c)); memcpy(b, c,
sizeof(c)); }
IR Testcase (C testcase run through -mem2reg):
define void @a(i8* %a, i8* %b) nounwind {
entry:
%c = alloca [100 x i8], align 1 ; <[100 x i8]*> [#uses=2]
%arraydecay = getelementptr inbounds [100 x i8]* %c, i32 0, i32 0 ; <i8*>
[#uses=1]
call void @llvm.memcpy.i32(i8* %arraydecay, i8* %a, i32 100, i32 1)
%arraydecay2 = getelementptr inbounds [100 x i8]* %c, i32 0, i32 0 ; <i8*>
[#uses=1]
call void @llvm.memcpy.i32(i8* %b, i8* %arraydecay2, i32 100, i32 1)
ret void
}
declare void @llvm.memcpy.i32(i8* nocapture, i8* nocapture, i32, i32) nounwind
Result of running -scalarrepl:
define void @a(i8* %a, i8* %b) nounwind {
entry:
%0 = bitcast i8* %a to i800* ; <i800*> [#uses=1]
%srcval1 = load i800* %0, align 1 ; <i800> [#uses=1]
%1 = bitcast i8* %b to i800* ; <i800*> [#uses=1]
store i800 %srcval1, i800* %1, align 1
ret void
}
The i800 load+store turns into completely nasty code, essentially an expanded
memmove.
Testcase derived from pattern seen in "embarassing" code examples.
--
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.
_______________________________________________
LLVMbugs mailing list
[email protected]
http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs
