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[PowerPC] Implement combineRepeatedFPDivisors
This does not matter on newer cores (where we can use reciprocal estimates in fast-math mode anyway), but for older cores this allows us to generate better fast-math code where we have multiple FDIVs with a common divisor. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222710 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -7526,6 +7526,28 @@ SDValue PPCTargetLowering::getRecipEstimate(SDValue Operand,
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return SDValue();
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}
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bool PPCTargetLowering::combineRepeatedFPDivisors(unsigned NumUsers) const {
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// Note: This functionality is used only when unsafe-fp-math is enabled, and
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// on cores with reciprocal estimates (which are used when unsafe-fp-math is
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// enabled for division), this functionality is redundant with the default
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// combiner logic (once the division -> reciprocal/multiply transformation
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// has taken place). As a result, this matters more for older cores than for
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// newer ones.
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// Combine multiple FDIVs with the same divisor into multiple FMULs by the
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// reciprocal if there are two or more FDIVs (for embedded cores with only
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// one FP pipeline) for three or more FDIVs (for generic OOO cores).
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switch (Subtarget.getDarwinDirective()) {
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default:
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return NumUsers > 2;
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case PPC::DIR_440:
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case PPC::DIR_A2:
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case PPC::DIR_E500mc:
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case PPC::DIR_E5500:
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return NumUsers > 1;
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}
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}
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static bool isConsecutiveLSLoc(SDValue Loc, EVT VT, LSBaseSDNode *Base,
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unsigned Bytes, int Dist,
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SelectionDAG &DAG) {
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@ -704,6 +704,7 @@ namespace llvm {
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bool &UseOneConstNR) const override;
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SDValue getRecipEstimate(SDValue Operand, DAGCombinerInfo &DCI,
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unsigned &RefinementSteps) const override;
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bool combineRepeatedFPDivisors(unsigned NumUsers) const override;
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CCAssignFn *useFastISelCCs(unsigned Flag) const;
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};
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39
test/CodeGen/PowerPC/fdiv-combine.ll
Normal file
39
test/CodeGen/PowerPC/fdiv-combine.ll
Normal file
@ -0,0 +1,39 @@
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; RUN: llc -mcpu=ppc64 < %s | FileCheck %s
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target datalayout = "E-m:e-i64:64-n32:64"
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target triple = "powerpc64-unknown-linux-gnu"
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; Following test case checks:
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; a / D; b / D; c / D;
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; =>
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; recip = 1.0 / D; a * recip; b * recip; c * recip;
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define void @three_fdiv_double(double %D, double %a, double %b, double %c) #0 {
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; CHECK-LABEL: three_fdiv_double:
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; CHECK: fdiv
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; CHECK-NEXT-NOT: fdiv
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; CHECK: fmul
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; CHECK: fmul
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; CHECK: fmul
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%div = fdiv double %a, %D
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%div1 = fdiv double %b, %D
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%div2 = fdiv double %c, %D
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tail call void @foo_3d(double %div, double %div1, double %div2)
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ret void
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}
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define void @two_fdiv_double(double %D, double %a, double %b) #0 {
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; CHECK-LABEL: two_fdiv_double:
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; CHECK: fdiv
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; CHECK: fdiv
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; CHECK-NEXT-NOT: fmul
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%div = fdiv double %a, %D
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%div1 = fdiv double %b, %D
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tail call void @foo_2d(double %div, double %div1)
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ret void
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}
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declare void @foo_3d(double, double, double)
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declare void @foo_3_2xd(<2 x double>, <2 x double>, <2 x double>)
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declare void @foo_2d(double, double)
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attributes #0 = { "unsafe-fp-math"="true" }
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