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llvm-project/llvm/test/Transforms/InstCombine/select-select.ll

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Remove a very old instcombine where we would turn sequences of selects into logical operations on the i1's driving them. This is a bad idea for every target I can think of (confirmed with micro tests on all of: x86-64, ARM, AArch64, Mips, and PowerPC) because it forces the i1 to be materialized into a general purpose register, whereas consuming it directly into a select generally allows it to exist only transiently in a predicate or flags register. Chandler ran a set of performance tests with this change, and reported no measurable change on x86-64. llvm-svn: 201275
2014-02-13 07:54:07 +08:00
; RUN: opt -instcombine -S < %s | FileCheck %s
; CHECK: @foo1
define float @foo1(float %a) #0 {
; CHECK-NOT: xor
%b = fcmp ogt float %a, 0.000000e+00
%c = select i1 %b, float %a, float 0.000000e+00
%d = fcmp olt float %c, 1.000000e+00
%f = select i1 %d, float %c, float 1.000000e+00
ret float %f
}
; CHECK: @foo2
define float @foo2(float %a) #0 {
; CHECK-NOT: xor
%b = fcmp ogt float %a, 0.000000e+00
%c = select i1 %b, float %a, float 0.000000e+00
%d = fcmp olt float %c, 1.000000e+00
%e = select i1 %b, float %a, float 0.000000e+00
%f = select i1 %d, float %e, float 1.000000e+00
ret float %f
}
attributes #0 = { nounwind readnone ssp uwtable }