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compiler: properly implement div and rem operations

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The division and remainder operations were lowered directly to LLVM IR.
This is wrong however because the Go specification defines exactly what
happens on a divide by zero or signed integer overflow and LLVM IR
itself treats those cases as undefined behavior. Therefore, this commit
implements divide by zero and signed integer overflow according to the
Go specification.

This does have an impact on the generated code, but it is surprisingly
small. I've used the drivers repo to test the code before and after, and
to my surprise most driver smoke tests are not changed at all. Those
that are, have only a small increase in code size. At the same time,
this change makes TinyGo more compliant to the Go specification.
This commit is contained in:
Ayke van Laethem
2021-10-21 00:42:03 +02:00
committed by Ron Evans
parent f99c600ad8
commit 86f1e6aec4
7 changed files with 169 additions and 10 deletions
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compiler/testdata/basic.ll
Vendored
+70
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@@ -28,6 +28,76 @@ entry:
ret i1 %0
}
; Function Attrs: nounwind
define hidden i32 @main.divInt(i32 %x, i32 %y, i8* %context, i8* %parentHandle) unnamed_addr #0 {
entry:
%0 = icmp eq i32 %y, 0
br i1 %0, label %divbyzero.throw, label %divbyzero.next
divbyzero.throw: ; preds = %entry
call void @runtime.divideByZeroPanic(i8* undef, i8* null) #0
unreachable
divbyzero.next: ; preds = %entry
%1 = icmp eq i32 %y, -1
%2 = icmp eq i32 %x, -2147483648
%3 = and i1 %1, %2
%4 = select i1 %3, i32 1, i32 %y
%5 = sdiv i32 %x, %4
ret i32 %5
}
declare void @runtime.divideByZeroPanic(i8*, i8*)
; Function Attrs: nounwind
define hidden i32 @main.divUint(i32 %x, i32 %y, i8* %context, i8* %parentHandle) unnamed_addr #0 {
entry:
%0 = icmp eq i32 %y, 0
br i1 %0, label %divbyzero.throw, label %divbyzero.next
divbyzero.throw: ; preds = %entry
call void @runtime.divideByZeroPanic(i8* undef, i8* null) #0
unreachable
divbyzero.next: ; preds = %entry
%1 = udiv i32 %x, %y
ret i32 %1
}
; Function Attrs: nounwind
define hidden i32 @main.remInt(i32 %x, i32 %y, i8* %context, i8* %parentHandle) unnamed_addr #0 {
entry:
%0 = icmp eq i32 %y, 0
br i1 %0, label %divbyzero.throw, label %divbyzero.next
divbyzero.throw: ; preds = %entry
call void @runtime.divideByZeroPanic(i8* undef, i8* null) #0
unreachable
divbyzero.next: ; preds = %entry
%1 = icmp eq i32 %y, -1
%2 = icmp eq i32 %x, -2147483648
%3 = and i1 %1, %2
%4 = select i1 %3, i32 1, i32 %y
%5 = srem i32 %x, %4
ret i32 %5
}
; Function Attrs: nounwind
define hidden i32 @main.remUint(i32 %x, i32 %y, i8* %context, i8* %parentHandle) unnamed_addr #0 {
entry:
%0 = icmp eq i32 %y, 0
br i1 %0, label %divbyzero.throw, label %divbyzero.next
divbyzero.throw: ; preds = %entry
call void @runtime.divideByZeroPanic(i8* undef, i8* null) #0
unreachable
divbyzero.next: ; preds = %entry
%1 = urem i32 %x, %y
ret i32 %1
}
; Function Attrs: nounwind
define hidden i1 @main.floatEQ(float %x, float %y, i8* %context, i8* %parentHandle) unnamed_addr #0 {
entry: