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Reapply r237453 with a fix for the test timeouts.
The test timeouts were due to instcombine fighting itself. Regression test added. Original log message: Canonicalize min/max expressions correctly. This patch introduces a canonical form for min/max idioms where one operand is extended or truncated. This often happens when the other operand is a constant. For example: %1 = icmp slt i32 %a, i32 0 %2 = sext i32 %a to i64 %3 = select i1 %1, i64 %2, i64 0 Would now be canonicalized into: %1 = icmp slt i32 %a, i32 0 %2 = select i1 %1, i32 %a, i32 0 %3 = sext i32 %2 to i64 This builds upon a patch posted by David Majenemer (https://www.marc.info/?l=llvm-commits&m=143008038714141&w=2). That pass passively stopped instcombine from ruining canonical patterns. This patch additionally actively makes instcombine canonicalize too. Canonicalization of expressions involving a change in type from int->fp or fp->int are not yet implemented. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237520 91177308-0d34-0410-b5e6-96231b3b80d8
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@@ -435,6 +435,15 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
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if (Instruction *Result = commonCastTransforms(CI))
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return Result;
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// Test if the trunc is the user of a select which is part of a
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// minimum or maximum operation. If so, don't do any more simplification.
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// Even simplifying demanded bits can break the canonical form of a
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// min/max.
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Value *LHS, *RHS;
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if (SelectInst *SI = dyn_cast<SelectInst>(CI.getOperand(0)))
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if (matchSelectPattern(SI, LHS, RHS) != SPF_UNKNOWN)
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return nullptr;
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// See if we can simplify any instructions used by the input whose sole
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// purpose is to compute bits we don't care about.
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if (SimplifyDemandedInstructionBits(CI))
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