[llvm] 2f15637 - [ValueTracking] Update `Ordered` when both operands are non-NaN. (#143349)

[via llvm-commits]

Author: Yingwei Zheng
Date: 2025-06-09T15:46:09+08:00
New Revision: 2f15637e04f51e3ef435c0c0d39aab0e8b933023

URL: https://github.com/llvm/llvm-project/commit/2f15637e04f51e3ef435c0c0d39aab0e8b933023
DIFF: https://github.com/llvm/llvm-project/commit/2f15637e04f51e3ef435c0c0d39aab0e8b933023.diff

LOG: [ValueTracking] Update `Ordered` when both operands are non-NaN. (#143349)

When the original predicate is ordered and both operands are non-NaN,
`Ordered` should be set to true. This variable still matters even if
both operands are non-NaN because FMF only applies to select, not fcmp.

Closes https://github.com/llvm/llvm-project/issues/143123.

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp
    llvm/test/Transforms/InstCombine/fcmp-select.ll
    llvm/unittests/Analysis/ValueTrackingTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d6bb852e208f9..d8c1096049dce 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -8660,6 +8660,7 @@ static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,
     if (LHSSafe && RHSSafe) {
       // Both operands are known non-NaN.
       NaNBehavior = SPNB_RETURNS_ANY;
+      Ordered = CmpInst::isOrdered(Pred);
     } else if (CmpInst::isOrdered(Pred)) {
       // An ordered comparison will return false when given a NaN, so it
       // returns the RHS.

diff  --git a/llvm/test/Transforms/InstCombine/fcmp-select.ll b/llvm/test/Transforms/InstCombine/fcmp-select.ll
index 053b233cb5f04..b622c8636eccb 100644
--- a/llvm/test/Transforms/InstCombine/fcmp-select.ll
+++ b/llvm/test/Transforms/InstCombine/fcmp-select.ll
@@ -270,12 +270,36 @@ define i1 @test_fcmp_select_var_const_unordered(double %x, double %y) {
 }
 
 define i1 @test_fcmp_ord_select_fcmp_oeq_var_const(double %x) {
-; CHECK-LABEL:    @test_fcmp_ord_select_fcmp_oeq_var_const(
-; CHECK-NEXT:     [[CMP1:%.*]] = fcmp oeq double [[X:%.*]], 1.000000e+00
-; CHECK-NEXT:     ret i1 [[CMP1]]
+; CHECK-LABEL: @test_fcmp_ord_select_fcmp_oeq_var_const(
+; CHECK-NEXT:    [[TMP1:%.*]] = fcmp oeq double [[X:%.*]], 1.000000e+00
+; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %cmp1 = fcmp ord double %x, 0.000000e+00
   %sel = select i1 %cmp1, double %x, double 0.000000e+00
   %cmp2 = fcmp oeq double %sel, 1.000000e+00
   ret i1 %cmp2
 }
+
+; Make sure that we recognize the SPF correctly.
+
+define float @test_select_nnan_nsz_fcmp_olt(float %x) {
+; CHECK-LABEL: @test_select_nnan_nsz_fcmp_olt(
+; CHECK-NEXT:    [[TMP1:%.*]] = fcmp olt float [[X:%.*]], -0.000000e+00
+; CHECK-NEXT:    [[SEL1:%.*]] = select i1 [[TMP1]], float [[X]], float -0.000000e+00
+; CHECK-NEXT:    ret float [[SEL1]]
+;
+  %cmp = fcmp olt float %x, 0.000000e+00
+  %sel = select nnan nsz i1 %cmp, float %x, float -0.000000e+00
+  ret float %sel
+}
+
+define float @test_select_nnan_nsz_fcmp_ult(float %x) {
+; CHECK-LABEL: @test_select_nnan_nsz_fcmp_ult(
+; CHECK-NEXT:    [[DOTINV:%.*]] = fcmp oge float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    [[SEL1:%.*]] = select i1 [[DOTINV]], float -0.000000e+00, float [[X]]
+; CHECK-NEXT:    ret float [[SEL1]]
+;
+  %cmp = fcmp ult float %x, 0.000000e+00
+  %sel = select nnan nsz i1 %cmp, float %x, float -0.000000e+00
+  ret float %sel
+}

diff  --git a/llvm/unittests/Analysis/ValueTrackingTest.cpp b/llvm/unittests/Analysis/ValueTrackingTest.cpp
index e23005b60891d..6031898f7f679 100644
--- a/llvm/unittests/Analysis/ValueTrackingTest.cpp
+++ b/llvm/unittests/Analysis/ValueTrackingTest.cpp
@@ -187,6 +187,15 @@ TEST_F(MatchSelectPatternTest, FastFMin) {
       "  %A = select i1 %1, float %a, float 5.0\n"
       "  ret float %A\n"
       "}\n");
+  expectPattern({SPF_FMINNUM, SPNB_RETURNS_ANY, true});
+}
+
+TEST_F(MatchSelectPatternTest, FastFMinUnordered) {
+  parseAssembly("define float @test(float %a) {\n"
+                "  %1 = fcmp nnan ult float %a, 5.0\n"
+                "  %A = select i1 %1, float %a, float 5.0\n"
+                "  ret float %A\n"
+                "}\n");
   expectPattern({SPF_FMINNUM, SPNB_RETURNS_ANY, false});
 }