[llvm] [InstCombine] Remove m_OneUse requirement only for max, not min (PR #81505)

Matt Arsenault via llvm-commits llvm-commits at lists.llvm.org
Mon Feb 26 02:53:27 PST 2024


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@@ -2288,11 +2288,18 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
 
     // max X, -X --> fabs X
     // min X, -X --> -(fabs X)
-    // TODO: Remove one-use limitation? That is obviously better for max.
-    //       It would be an extra instruction for min (fnabs), but that is
-    //       still likely better for analysis and codegen.
-    if ((match(Arg0, m_OneUse(m_FNeg(m_Value(X)))) && Arg1 == X) ||
-        (match(Arg1, m_OneUse(m_FNeg(m_Value(X)))) && Arg0 == X)) {
+    // TODO: Remove one-use limitation? That is obviously better for max,
+    // hence why we don't check for one-use for that. However,
+    // it would be an extra instruction for min (fnabs), but
+    // that is still likely better for analysis and codegen.
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arsenm wrote:

we could special case this in computeKnownFPClass too 

https://github.com/llvm/llvm-project/pull/81505


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