Revert some auto-generated checks where a wildcard was needed

[andrew.w.kaylor]

Summary

This change reverts a batch of autogenerated checks in the pow-exp.ll file where a previous version had used wildcards to account for minor variations in constant folding by different math libraries. The file is also updated to add a comment that will prevent future autogeneration.

The autogenerated changes being reverted are among the changes here: https://github.com/intel-restricted/applications.compilers.llvm-project/commit/2caaec65c04ea7d0e9568b7895b7a46d6100cb75#diff-e800a6ae456ef1224d5a4e6f1f5145732f36b4f84b21d35c671c14ca7d158364

See: https://discourse.llvm.org/t/auto-generated-checks-with-inexact-fp-results/71713

[nikic]

Can you change the constants to values that don't suffer from accuracy problems instead?

[andrew.w.kaylor]

In D158758#4614632, @nikic wrote:

Can you change the constants to values that don't suffer from accuracy problems instead?

I don't think so -- at least not in all cases. For example, some of these checks are verifying that the pow(C,x) -> exp2(log2(C)*x) transformation happens in the presence of fast-math flags. If the computation returns an exact result, the fast-math flag isn't required.

Example: https://godbolt.org/z/MxjYbs6Ys

[nikic]

LGTM

llvm/test/Transforms/InstCombine/pow-exp.ll

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; NOTE: Do not autogenerate
+;       Assertions were previously autogenerated by utils/update_test_checks.py
+;       but some hand modifications were needed to account for rounding errors
+;       in constant folding that depend on the compiler's math library version.
 ; RUN: opt < %s -passes=instcombine -S | FileCheck %s
 
 define float @powf_expf(float %x, float %y) {
 ; CHECK-LABEL: @powf_expf(
 ; CHECK-NEXT:    [[MUL:%.*]] = fmul fast float [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    [[EXP:%.*]] = call fast float @llvm.exp.f32(float [[MUL]])
 ; CHECK-NEXT:    ret float [[EXP]]
 ;

 
 ; pow(C,x) -> exp2(log2(C)*x)
 
 declare void @use_d(double)
 declare void @use_f(float)
 
 define double @pow_ok_base(double %e) {
 ; CHECK-LABEL: @pow_ok_base(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0xBFE0776228967D13
+; Do not change 0xBFE0776{{.*}} to the exact constant, see PR42740
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0xBFE0776{{.*}}
 ; CHECK-NEXT:    [[EXP2:%.*]] = tail call nnan ninf afn double @exp2(double [[MUL]])
 ; CHECK-NEXT:    ret double [[EXP2]]
 ;
-; Do not change 0xBFE0776{{.*}} to the exact constant, see PR42740
   %call = tail call afn nnan ninf double @pow(double 0x3FE6666666666666, double %e)
   ret double %call
 }
 
 define double @pow_ok_base_fast(double %e) {
 ; CHECK-LABEL: @pow_ok_base_fast(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul fast double [[E:%.*]], 0xBFE0776228967D13
+; CHECK-NEXT:    [[MUL:%.*]] = fmul fast double [[E:%.*]], 0xBFE0776{{.*}}
 ; CHECK-NEXT:    [[EXP2:%.*]] = tail call fast double @exp2(double [[MUL]])
 ; CHECK-NEXT:    ret double [[EXP2]]
 ;
   %call = tail call fast double @pow(double 0x3FE6666666666666, double %e)
   ret double %call
 }
 
 define double @pow_ok_base2(double %e) {
 ; CHECK-LABEL: @pow_ok_base2(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0x4010952C788751AC
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0x4010952{{.*}}
 ; CHECK-NEXT:    [[EXP2:%.*]] = tail call nnan ninf afn double @exp2(double [[MUL]])
 ; CHECK-NEXT:    ret double [[EXP2]]
 ;
   %call = tail call afn nnan ninf double @pow(double 1.770000e+01, double %e)
   ret double %call
 }
 
 define double @pow_ok_base3(double %e) {
 ; CHECK-LABEL: @pow_ok_base3(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0x400AB0B5584886CD
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0x400AB0B5{{.*}}
 ; CHECK-NEXT:    [[EXP2:%.*]] = tail call nnan ninf afn double @exp2(double [[MUL]])
 ; CHECK-NEXT:    ret double [[EXP2]]
 ;
   %call = tail call afn nnan ninf double @pow(double 1.010000e+01, double %e)
   ret double %call
 }
 
 define double @pow_ok_ten_base(double %e) {
 ; CHECK-LABEL: @pow_ok_ten_base(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0x400A934F0979A371
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0x400A934F{{.*}}
 ; CHECK-NEXT:    [[EXP2:%.*]] = tail call nnan ninf afn double @exp2(double [[MUL]])
 ; CHECK-NEXT:    ret double [[EXP2]]
 ;
   %call = tail call afn nnan ninf double @pow(double 1.000000e+01, double %e)
   ret double %call
 }
 
 define double @pow_ok_denorm_base(double %e) {
 ; CHECK-LABEL: @pow_ok_denorm_base(
 ; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0xC0904800000005C5
 ; CHECK-NEXT:    [[EXP2:%.*]] = tail call nnan ninf afn double @exp2(double [[MUL]])
 ; CHECK-NEXT:    ret double [[EXP2]]
 ;
   %call = tail call afn nnan ninf double @pow(double 0x00000000FFFFFFFF, double %e)
   ret double %call
 }
 
 define float @powf_ok_base(float %e) {
 ; CHECK-LABEL: @powf_ok_base(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn float [[E:%.*]], 0xBFE0776240000000
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn float [[E:%.*]], 0xBFE07762{{.*}}
 ; CHECK-NEXT:    [[EXP2F:%.*]] = tail call nnan ninf afn float @exp2f(float [[MUL]])
 ; CHECK-NEXT:    ret float [[EXP2F]]
 ;
   %call = tail call afn nnan ninf float @powf(float 0x3FE6666660000000, float %e)
   ret float %call
 }
 
 define float @powf_ok_base2(float %e) {
 ; CHECK-LABEL: @powf_ok_base2(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn float [[E:%.*]], 0x4010952C80000000
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn float [[E:%.*]], 0x4010952{{.*}}
 ; CHECK-NEXT:    [[EXP2F:%.*]] = tail call nnan ninf afn float @exp2f(float [[MUL]])
 ; CHECK-NEXT:    ret float [[EXP2F]]
 ;
   %call = tail call afn nnan ninf float @powf(float 0x4031B33340000000, float %e)
   ret float %call
 }
 
 define float @powf_ok_base3(float %e) {
 ; CHECK-LABEL: @powf_ok_base3(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn float [[E:%.*]], 0x400AB0B560000000
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn float [[E:%.*]], 0x400AB0B5{{.*}}
 ; CHECK-NEXT:    [[EXP2F:%.*]] = tail call nnan ninf afn float @exp2f(float [[MUL]])
 ; CHECK-NEXT:    ret float [[EXP2F]]
 ;
   %call = tail call afn nnan ninf float @powf(float 0x4024333340000000, float %e)
   ret float %call
 }
 
 define float @powf_ok_ten_base(float %e) {
 ; CHECK-LABEL: @powf_ok_ten_base(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn float [[E:%.*]], 0x400A934F00000000
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn float [[E:%.*]], 0x400A934{{.*}}
 ; CHECK-NEXT:    [[EXP2F:%.*]] = tail call nnan ninf afn float @exp2f(float [[MUL]])
 ; CHECK-NEXT:    ret float [[EXP2F]]
 ;
   %call = tail call afn nnan ninf float @powf(float 1.000000e+01, float %e)
   ret float %call
 }
 
 define float @powf_ok_denorm_base(float %e) {

 ; CHECK-NEXT:    ret double [[CALL]]
 ;
   %call = tail call afn nnan ninf double @pow(double -4.000000e+00, double %e)
   ret double %call
 }
 
 define double @pow_multiuse(double %e) {
 ; CHECK-LABEL: @pow_multiuse(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0x4002934F0979A371
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn double [[E:%.*]], 0x4002934{{.*}}
 ; CHECK-NEXT:    [[EXP2:%.*]] = tail call nnan ninf afn double @exp2(double [[MUL]])
 ; CHECK-NEXT:    tail call void @use_d(double [[EXP2]])
 ; CHECK-NEXT:    ret double [[EXP2]]
 ;
   %call = tail call afn nnan ninf double @pow(double 5.000000e+00, double %e)
   tail call void @use_d(double %call)
   ret double %call
 }

 ; CHECK-NEXT:    ret double [[CALL]]
 ;
   %call = tail call afn ninf double @pow(double 0x3FE6666666666666, double %e)
   ret double %call
 }
 
 define double @pow_ok_base_no_ninf(double %e) {
 ; CHECK-LABEL: @pow_ok_base_no_ninf(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan afn double [[E:%.*]], 0xBFE0776228967D13
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan afn double [[E:%.*]], 0xBFE0776{{.*}}
 ; CHECK-NEXT:    [[EXP2:%.*]] = tail call nnan afn double @exp2(double [[MUL]])
 ; CHECK-NEXT:    ret double [[EXP2]]
 ;
   %call = tail call afn nnan double @pow(double 0x3FE6666666666666, double %e)
   ret double %call
 }
 
 define float @powf_zero_base(float %e) {

 ; CHECK-NEXT:    ret float [[CALL]]
 ;
   %call = tail call afn nnan ninf float @powf(float -4.000000e+00, float %e)
   ret float %call
 }
 
 define float @powf_multiuse(float %e) {
 ; CHECK-LABEL: @powf_multiuse(
-; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn float [[E:%.*]], 0x4002934F00000000
+; CHECK-NEXT:    [[MUL:%.*]] = fmul nnan ninf afn float [[E:%.*]], 0x4002934{{.*}}
 ; CHECK-NEXT:    [[EXP2F:%.*]] = tail call nnan ninf afn float @exp2f(float [[MUL]])
 ; CHECK-NEXT:    tail call void @use_f(float [[EXP2F]])
 ; CHECK-NEXT:    ret float [[EXP2F]]
 ;
   %call = tail call afn nnan ninf float @powf(float 5.000000e+00, float %e)
   tail call void @use_f(float %call)
   ret float %call
 }