[InstCombine][InstSimplify] add tests for sign of maxnum; NFC

More coverage for D83601.

Author: rotateright

llvm/test/Transforms/InstCombine/copysign.ll

@@ -3,6 +3,7 @@
 
 declare float @llvm.fabs.f32(float)
 declare float @llvm.copysign.f32(float, float)
+declare float @llvm.maxnum.f32(float, float)
 declare <3 x double> @llvm.copysign.v3f64(<3 x double>, <3 x double>)
 
 define float @positive_sign_arg(float %x) {
@@ -63,6 +64,18 @@ define <3 x double> @known_positive_sign_arg_vec(<3 x double> %x, <3 x i32> %y)
   ret <3 x double> %r
 }
 
+; FIXME: maxnum(-0.0, 0.0) can return -0.0.
+
+define float @not_known_positive_sign_arg(float %x, float %y) {
+; CHECK-LABEL: @not_known_positive_sign_arg(
+; CHECK-NEXT:    [[TMP1:%.*]] = call ninf float @llvm.fabs.f32(float [[Y:%.*]])
+; CHECK-NEXT:    ret float [[TMP1]]
+;
+  %max = call float @llvm.maxnum.f32(float %x, float 0.0)
+  %r = call ninf float @llvm.copysign.f32(float %y, float %max)
+  ret float %r
+}
+
 ; The magnitude operand of the 1st copysign is irrelevant.
 ; copysign(x, copysign(y, z)) --> copysign(x, z)
 

llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll

@@ -1383,3 +1383,13 @@ define float @maxnum_with_negzero_op_commute(float %a) {
   %fabs = call float @llvm.fabs.f32(float %max)
   ret float %fabs
 }
+
+define float @maxnum_with_pos_one_op(float %a) {
+; CHECK-LABEL: @maxnum_with_pos_one_op(
+; CHECK-NEXT:    [[MAX:%.*]] = call float @llvm.maxnum.f32(float [[A:%.*]], float 1.000000e+00)
+; CHECK-NEXT:    ret float [[MAX]]
+;
+  %max = call float @llvm.maxnum.f32(float %a, float 1.0)
+  %fabs = call float @llvm.fabs.f32(float %max)
+  ret float %fabs
+}

llvm/test/Transforms/InstSimplify/floating-point-compare.ll

@@ -212,6 +212,15 @@ define i1 @orderedLessZero_fdiv(float %x) {
   ret i1 %uge
 }
 
+define i1 @orderedLessZero_maxnum(float %x) {
+; CHECK-LABEL: @orderedLessZero_maxnum(
+; CHECK-NEXT:    ret i1 true
+;
+  %d = call float @llvm.maxnum.f32(float %x, float 0.0)
+  %uge = fcmp uge float %d, 0.0
+  ret i1 %uge
+}
+
 define i1 @orderedLessZeroExpExt(float) {
 ; CHECK-LABEL: @orderedLessZeroExpExt(
 ; CHECK-NEXT:    ret i1 true