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author | Owen Anderson <resistor@mac.com> | 2014-02-12 23:54:07 +0000 |
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committer | Owen Anderson <resistor@mac.com> | 2014-02-12 23:54:07 +0000 |
commit | 3042a65e5f37ecd3fdf0c97133bc1e1a3f12766f (patch) | |
tree | d8c7ff09149d53186da397f6e113b33fe59338eb /lib/Transforms/InstCombine/InstCombineCompares.cpp | |
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 'lib/Transforms/InstCombine/InstCombineCompares.cpp')
-rw-r--r-- | lib/Transforms/InstCombine/InstCombineCompares.cpp | 25 |
1 files changed, 0 insertions, 25 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index 5dd3325a0b..281ff4050c 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -3313,31 +3313,6 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) { if (Instruction *NV = FoldFCmp_IntToFP_Cst(I, LHSI, RHSC)) return NV; break; - case Instruction::Select: { - // If either operand of the select is a constant, we can fold the - // comparison into the select arms, which will cause one to be - // constant folded and the select turned into a bitwise or. - Value *Op1 = 0, *Op2 = 0; - if (LHSI->hasOneUse()) { - if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) { - // Fold the known value into the constant operand. - Op1 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC); - // Insert a new FCmp of the other select operand. - Op2 = Builder->CreateFCmp(I.getPredicate(), - LHSI->getOperand(2), RHSC, I.getName()); - } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) { - // Fold the known value into the constant operand. - Op2 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC); - // Insert a new FCmp of the other select operand. - Op1 = Builder->CreateFCmp(I.getPredicate(), LHSI->getOperand(1), - RHSC, I.getName()); - } - } - - if (Op1) - return SelectInst::Create(LHSI->getOperand(0), Op1, Op2); - break; - } case Instruction::FSub: { // fcmp pred (fneg x), C -> fcmp swap(pred) x, -C Value *Op; |