[PATCH] [InstCombine] Add a new formula for SMIN.
Sanjoy Das
sanjoy at playingwithpointers.com
Wed Apr 29 21:59:35 PDT 2015
REPOSITORY
rL LLVM
http://reviews.llvm.org/D9352
Files:
llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
llvm/trunk/test/Transforms/InstCombine/select.ll
Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -86,6 +86,17 @@
return (CmpLHS == FalseVal) ? SPF_ABS : SPF_NABS;
}
}
+
+ // Y >s C ? ~Y : ~C == ~Y <s ~C ? ~Y : ~C = SMIN(~Y, ~C)
+ if (const auto *C2 = dyn_cast<ConstantInt>(FalseVal)) {
+ if (C1->getType() == C2->getType() && ~C1->getValue() == C2->getValue() &&
+ (match(TrueVal, m_Not(m_Specific(CmpLHS))) ||
+ match(CmpLHS, m_Not(m_Specific(TrueVal))))) {
+ LHS = TrueVal;
+ RHS = FalseVal;
+ return SPF_SMIN;
+ }
+ }
}
// TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5)
Index: llvm/trunk/test/Transforms/InstCombine/select.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/select.ll
+++ llvm/trunk/test/Transforms/InstCombine/select.ll
@@ -1520,3 +1520,15 @@
%s1 = select i1 %c1, i32 %r0, i32 %s0
ret i32 %s1
}
+
+define i32 @test_max_of_min(i32 %a) {
+; MAX(MIN(%a, -1), -1) == -1
+; CHECK-LABEL: @test_max_of_min(
+; CHECK: ret i32 -1
+ %not_a = xor i32 %a, -1
+ %c0 = icmp sgt i32 %a, 0
+ %s0 = select i1 %c0, i32 %not_a, i32 -1
+ %c1 = icmp sgt i32 %s0, -1
+ %s1 = select i1 %c1, i32 %s0, i32 -1
+ ret i32 %s1
+}
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