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author | Dan Gohman <gohman@apple.com> | 2008-09-16 18:46:06 +0000 |
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committer | Dan Gohman <gohman@apple.com> | 2008-09-16 18:46:06 +0000 |
commit | 81b28ceab6bd0ed6a784b7dc952ddb0b03fc6de7 (patch) | |
tree | 057a8a72e899e9640c6b3892016da39c468f4fa6 /test/Transforms/InstCombine/preserve-sminmax.ll | |
parent | 19a341acb8df340651053c1ebb2403232103445b (diff) | |
download | external_llvm-81b28ceab6bd0ed6a784b7dc952ddb0b03fc6de7.zip external_llvm-81b28ceab6bd0ed6a784b7dc952ddb0b03fc6de7.tar.gz external_llvm-81b28ceab6bd0ed6a784b7dc952ddb0b03fc6de7.tar.bz2 |
Improve instcombine's handling of integer min and max in two ways:
- Recognize expressions like "x > -1 ? x : 0" as min/max and turn them
into expressions like "x < 0 ? 0 : x", which is easily recognizable
as a min/max operation.
- Refrain from folding expression like "y/2 < 1" to "y < 2" when the
comparison is being used as part of a min or max idiom, like
"y/2 < 1 ? 1 : y/2". In that case, the division has another use, so
folding doesn't eliminate it, and obfuscates the min/max, making it
harder to recognize as a min/max operation.
These benefit ScalarEvolution, CodeGen, and anything else that wants to
recognize integer min and max.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56246 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test/Transforms/InstCombine/preserve-sminmax.ll')
-rw-r--r-- | test/Transforms/InstCombine/preserve-sminmax.ll | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/test/Transforms/InstCombine/preserve-sminmax.ll b/test/Transforms/InstCombine/preserve-sminmax.ll new file mode 100644 index 0000000..24fb7da --- /dev/null +++ b/test/Transforms/InstCombine/preserve-sminmax.ll @@ -0,0 +1,22 @@ +; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep { i32 \[%\]sd, \[\[:alnum:\]\]* \\?1\\>} | count 4 + +; Instcombine normally would fold the sdiv into the comparison, +; making "icmp slt i32 %h, 2", but in this case the sdiv has +; another use, so it wouldn't a big win, and it would also +; obfuscate an otherise obvious smax pattern to the point where +; other analyses wouldn't recognize it. + +define i32 @foo(i32 %h) { + %sd = sdiv i32 %h, 2 + %t = icmp slt i32 %sd, 1 + %r = select i1 %t, i32 %sd, i32 1 + ret i32 %r +} + +define i32 @bar(i32 %h) { + %sd = sdiv i32 %h, 2 + %t = icmp sgt i32 %sd, 1 + %r = select i1 %t, i32 %sd, i32 1 + ret i32 %r +} + |