forked from OSchip/llvm-project
f50aa6ae5c
I noticed this in the code compiled for a routine using std::map, which produced this code: %25 = tail call i32 @memcmp(i8* %24, i8* %23, i32 6) nounwind readonly %.lobit.i = lshr i32 %25, 31 ; <i32> [#uses=1] %tmp.i = trunc i32 %.lobit.i to i8 ; <i8> [#uses=1] %toBool = icmp eq i8 %tmp.i, 0 ; <i1> [#uses=1] br i1 %toBool, label %bb3, label %bb4 which compiled to: call L_memcmp$stub shrl $31, %eax testb %al, %al jne LBB1_11 ## with this change, we compile it to: call L_memcmp$stub testl %eax, %eax js LBB1_11 This triggers all the time in common code, with patters like this: %169 = and i32 %ply, 1 ; <i32> [#uses=1] %170 = trunc i32 %169 to i8 ; <i8> [#uses=1] %toBool = icmp ne i8 %170, 0 ; <i1> [#uses=1] %7 = lshr i32 %6, 24 ; <i32> [#uses=1] %9 = trunc i32 %7 to i8 ; <i8> [#uses=1] %10 = icmp ne i8 %9, 0 ; <i1> [#uses=1] etc llvm-svn: 61985 |
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