diff options
author | Owen Anderson <resistor@mac.com> | 2014-02-12 23:54:07 +0000 |
---|---|---|
committer | Owen Anderson <resistor@mac.com> | 2014-02-12 23:54:07 +0000 |
commit | 3042a65e5f37ecd3fdf0c97133bc1e1a3f12766f (patch) | |
tree | d8c7ff09149d53186da397f6e113b33fe59338eb /test | |
parent | 029a76b0a26981afb6bc3252b2a75b16393d893e (diff) | |
download | llvm-3042a65e5f37ecd3fdf0c97133bc1e1a3f12766f.tar.gz llvm-3042a65e5f37ecd3fdf0c97133bc1e1a3f12766f.tar.bz2 llvm-3042a65e5f37ecd3fdf0c97133bc1e1a3f12766f.tar.xz |
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201275 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test')
-rw-r--r-- | test/Transforms/InstCombine/select-select.ll | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/test/Transforms/InstCombine/select-select.ll b/test/Transforms/InstCombine/select-select.ll new file mode 100644 index 0000000000..65820acf07 --- /dev/null +++ b/test/Transforms/InstCombine/select-select.ll @@ -0,0 +1,24 @@ +; 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 } |