Bug 7953 – DMD Error: variable r used before set when compiling with -O

When compiling this code with dmd -O it says: test.d(55) Error: variable r used before set i might have overlooked something, but shouldn't that compile? dmd 2.059 here. import std.stdio; import std.math; import core.simd; import std.datetime; import std.conv; /** Benchmarks: suicide@zoaHTPC /media/code $ dmd test.d _VEC: [TickDuration(2014413920)] SIMD: [TickDuration(2057610817)] suicide@zoaHTPC /media/code $ dmd test.d -O _VEC: [TickDuration(1589025986)] SIMD: [TickDuration(2050198165)] suicide@zoaHTPC /media/code $ dmd test.d -O -release _VEC: [TickDuration(1738538836)] SIMD: [TickDuration(1172608340)] suicide@zoaHTPC /media/code $ dmd test.d -O -release -inline _VEC: [TickDuration(1570424587)] SIMD: [TickDuration(1184942170)] suicide@zoaHTPC /media/code $ dmd test.d -O -release -noboundscheck _VEC: [TickDuration(752330929)] SIMD: [TickDuration(1128528117)] */ string gen(int D) { string s; for(size_t i = 0; i < D-1; i+=4) { s ~= "v1.array = a1["~to!string(i)~".."~to!string(i+4)~"];"; s ~= "v2.array = a2["~to!string(i)~".."~to!string(i+4)~"];"; s ~= "r = __simd(XMM.ADDPS, v1,v2);"; //~ s ~= "res["~to!string(i)~".."~to!string(i+4)~"] = r.array;"; s ~= "res.ptr["~to!string(i)~"] = r.ptr["~to!string(i)~"];"; s ~= "res.ptr["~to!string(i+1)~"] = r.ptr["~to!string(i+1)~"];"; s ~= "res.ptr["~to!string(i+2)~"] = r.ptr["~to!string(i+2)~"];"; s ~= "res.ptr["~to!string(i+3)~"] = r.ptr["~to!string(i+3)~"];"; } return s; } T[D] simdAdd(T, int D)(T[D] a1, T[D] a2) { T[D] res; float4 v1; float4 v2; float4 r; //writeln(gen(D)); mixin(gen(D)); return res; } T[D] addV(T, int D)(T[D] a1, T[D] a2) { T[D] r; //foreach(x;0..10) foreach(i;0..D) r[i] = a1[i]+a2[i]; return r; } void main() { float[8] v1 = [1,2,3,4,1,2,3,4]; float[8] v2 = [1,2,3,4,1,2,3,4]; void test1(){addV(v1,v2);} void test2(){simdAdd(v1,v2);} // test2(); //~ writeln("STD: ", benchmark!(addS!(int,4)([1,2,3,4],[1,2,3,4]))(10_000_000)); writeln("_VEC: ", benchmark!(test1)(10_000_000)); writeln("SIMD: ", benchmark!(test2)(10_000_000)); }

first one: suicide@zoaHTPC /media/code $ dmd test.d -release -noboundscheck -O test.d(55): Error: variable r used before set another one: suicide@zoaHTPC /media/code $ dmd test.d -release -noboundscheck -O -inline /usr/include/phobos2/std/datetime.d(29600): Error: variable std.path.sep is depr ecated /usr/include/phobos2/std/datetime.d(29601): Error: variable std.path.sep is depr ecated /usr/include/phobos2/std/path.d(2715): Error: alias std.path.onOutOfMemoryError is deprecated

Please reduce your code to the minimum that shows the behaviour.

I've reduced the test case to this: import core.simd; import std.conv; string gen(int D) { string s; s ~= "r = __simd(XMM.ADDPS, v1,v2);"; return "res.ptr["~to!string(0)~"] = r.ptr["~to!string(0)~"];"; } T[D] simdAdd(T, int D)(T[D] a1, T[D] a2) { T[D] res; float4 r; mixin(gen(D)); return res; } void main() { float[8] v1 = [1,2,3,4,1,2,3,4]; float[8] v2 = [1,2,3,4,1,2,3,4]; simdAdd(v1,v2); } but I can't reproduce the error message, so maybe I've overlooked something. However, interestingly, this compiles with -O flag and crashes the compiler without. PS E:\DigitalMars\dmd2\samples> rdmd bug.d Internal error: ..\ztc\cg87.c 1699 PS E:\DigitalMars\dmd2\samples> rdmd -O bug.d PS E:\DigitalMars\dmd2\samples>

(In reply to comment #3) > I've reduced the test case to this: > > ... > > but I can't reproduce the error message, so maybe I've overlooked something. > However, interestingly, this compiles with -O flag and crashes the compiler > without. > > PS E:\DigitalMars\dmd2\samples> rdmd bug.d > Internal error: ..\ztc\cg87.c 1699 > PS E:\DigitalMars\dmd2\samples> rdmd -O bug.d > PS E:\DigitalMars\dmd2\samples> The ICE may be related to issue 7951.

(In reply to comment #0) > When compiling this code with dmd -O it says: > test.d(55) Error: variable r used before set > i might have overlooked something, but shouldn't that compile? I tried to test on Windows. I suppose this is an _expected_ behavior. Maybe, 'r.ptr[4]' and its followings lines should be 'r.ptr[0]' and so on. Please help, SIMD expert... :) ================================================================== Reduced Code: //DMDFLAGS=-O -m64 import core.simd; alias float[8] F8; F8 simdAdd(F8 a1, F8 a2) { F8 res; float4 v1; float4 v2; float4 r; // 0..4 OK v1.array = a1[0..4]; v2.array = a2[0..4]; r = __simd(XMM.ADDPS, v1,v2); res.ptr[0] = r.ptr[0]; res.ptr[1] = r.ptr[1]; res.ptr[2] = r.ptr[2]; res.ptr[3] = r.ptr[3]; // 4..8 NG v1.array = a1[4..8]; v2.array = a2[4..8]; r = __simd(XMM.ADDPS, v1,v2); res.ptr[4] = r.ptr[4]; // Error: variable r used before set res.ptr[5] = r.ptr[5]; res.ptr[6] = r.ptr[6]; res.ptr[7] = r.ptr[7]; return res; }

float4 r; ... res.ptr[4] = r.ptr[4]; // Error: variable r used before set The error here is that there are only 4 entries in float4, and you're indexing the 5th one. If the function is marked @safe, it won't compile. Not a compiler bug.

(In reply to SomeDude from comment #3) > but I can't reproduce the error message, so maybe I've overlooked something. > However, interestingly, this compiles with -O flag and crashes the compiler > without. > > PS E:\DigitalMars\dmd2\samples> rdmd bug.d > Internal error: ..\ztc\cg87.c 1699 This works without error in the current compiler.