[llvm-dev] Optimizing functions using logical operators

[Stéphane Letz via llvm-dev]

Hi,

I’m looking at what the LLVM compilation chain does to optimize the following functions using logical operators. The one using integer type (t1 and t3) are optimized, but not the ones using float type (t2 and t4), even when using -O3 or -Ofast.  Why is that ? 

Thera are those kind of optimizations done in the LLVM source code?

Thanks.


bool t1(int v1)
{
    return (2 + v1) == 7;
}

bool t2(float v1)
{
    return (2.f + v1) == 7.f;
}

bool t3(int v1)
{
    return (2 * v1) > 0;
}

bool t4(float v1)
{
    return (2.f * v1) > 0;
}

; Function Attrs: norecurse nounwind readnone ssp uwtable
define zeroext i1 @_Z2t1i(i32) #0 {
  %2 = icmp eq i32 %0, 5
  ret i1 %2
}

; Function Attrs: norecurse nounwind readnone ssp uwtable
define zeroext i1 @_Z2t2f(float) #0 {
  %2 = fadd float %0, 2.000000e+00
  %3 = fcmp oeq float %2, 7.000000e+00
  ret i1 %3
}

; Function Attrs: norecurse nounwind readnone ssp uwtable
define zeroext i1 @_Z2t3i(i32) #0 {
  %2 = icmp sgt i32 %0, 0
  ret i1 %2
}

; Function Attrs: norecurse nounwind readnone ssp uwtable
define zeroext i1 @_Z2t4f(float) #0 {
  %2 = fmul float %0, 2.000000e+00
  %3 = fcmp ogt float %2, 0.000000e+00
  ret i1 %3
}