Bug 7391 – floating wtf dmd 2.057 64 bit

------------------------------------------------- + The complete source files. ------------------------------------------------- import std.stdio; void calculate1(float a, float b) { float s1 = 1.0f - a; float s2 = a * b; writeln(s2); writeln(a * b); } void calculate2(float a, float b) { float s1 = 1.0 - a; float s2 = a * b; writeln(s2); writeln(a * b); } void calculate3(double a, double b) { double s1 = 1.0 - a; double s2 = a * b; writeln(s2); writeln(a * b); } int main() { writeln("calculate1:"); calculate1(0.75f,2.0f); writeln("calculate2:"); calculate2(0.75f,2.0f); writeln("calculate3:"); calculate3(0.75f,2.0f); return 0; } ------------------------------------------------- + The complete output ------------------------------------------------- calculate1: 1.5 1.5 calculate2: 0 1.5 calculate3: 1.5 1.5 ------------------------------------------------- + Compiler ------------------------------------------------- DMD64 D Compiler v2.057 Copyright (c) 1999-2011 by Digital Mars written by Walter Bright Documentation: http://www.digitalmars.com/d/2.0/index.html Usage: This is from the downloaded zip file. I'm using eclipse to compile it. Added the -debug. ------------------------------------------------- + Ubuntu 11.10 64 bit ------------------------------------------------- uname -r 3.0.0-15-generic ------------------------------------------------- + BEHAVIOUR ------------------------------------------------- Seems to work on 32 bit on windows. And also when you use -inline on the compiler. (even on 64 bit with inline) In the previous message here below is the assembly output of calculate2. Pay close attention to the cvtss2sd, the cvtsd2ss and the mulss. float s1 = 1.0 - a; float s2 = a * b; The first mulss (s2) uses the xmm1 register. Which was subjected to the cvtss2sd for the (s1) calculation. ------------------------------------------------- + objdump -S test1.o ------------------------------------------------- This is the assembly output of: void calculate2(float a, float b) Warning: mov is from left to right. :-) 0000000000000000 <_D4main10calculate2FffZv>: 0: 55 push %rbp 1: 48 8b ec mov %rsp,%rbp 4: 48 83 ec 20 sub $0x20,%rsp 8: f3 0f 11 45 f0 movss %xmm0,-0x10(%rbp) d: f3 0f 11 4d f8 movss %xmm1,-0x8(%rbp) 12: 48 b8 00 00 00 00 00 movabs $0x3ff0000000000000,%rax 19: 00 f0 3f 1c: 48 89 45 e0 mov %rax,-0x20(%rbp) 20: f2 0f 10 55 e0 movsd -0x20(%rbp),%xmm2 25: f3 0f 5a c9 cvtss2sd %xmm1,%xmm1 29: f2 0f 5c d1 subsd %xmm1,%xmm2 2d: f2 0f 5a d2 cvtsd2ss %xmm2,%xmm2 31: f3 0f 59 c8 mulss %xmm0,%xmm1 35: f3 0f 11 4d e8 movss %xmm1,-0x18(%rbp) 3a: f3 0f 10 45 e8 movss -0x18(%rbp),%xmm0 3f: e8 00 00 00 00 callq 44 <_D4main10calculate2FffZv+0x44> 44: f3 0f 10 45 f8 movss -0x8(%rbp),%xmm0 49: f3 0f 10 4d f0 movss -0x10(%rbp),%xmm1 4e: f3 0f 59 c1 mulss %xmm1,%xmm0 52: e8 00 00 00 00 callq 57 <_D4main10calculate2FffZv+0x57> 57: c9 leaveq 58: c3 retq 59: 90 nop 5a: 90 nop 5b: 90 nop

(In reply to comment #0) > ------------------------------------------------- > + The complete source files. > ------------------------------------------------- Sometimes you need a some determination and even a bit of stubborness to have a bug fixed :-)

I've closed this before. It works correctly on the current build of dmd. Also, in the future, please indicate what dmd switches were used to do the compile.