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compiler: truncate shift amount when needed

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Ayke van Laethem
2018-09-03 00:22:55 +02:00
parent ebd87ce4cd
commit 4ed04309a3
1 changed files with 7 additions and 0 deletions
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compiler.go
+7
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@@ -2108,6 +2108,13 @@ func (c *Compiler) parseBinOp(frame *Frame, binop *ssa.BinOp) (llvm.Value, error
// x and y must have equal sizes, make Y bigger in this case. // x and y must have equal sizes, make Y bigger in this case.
// y is unsigned, this has been checked by the Go type checker. // y is unsigned, this has been checked by the Go type checker.
y = c.builder.CreateZExt(y, x.Type(), "") y = c.builder.CreateZExt(y, x.Type(), "")
} else if sizeX < sizeY {
// What about shifting more than the integer width?
// I'm not entirely sure what the Go spec is on that, but as
// Intel CPUs have undefined behavior when shifting more
// than the integer width I'm assuming it is also undefined
// in Go.
y = c.builder.CreateTrunc(y, x.Type(), "")
} }
switch binop.Op { switch binop.Op {
case token.SHL: // << case token.SHL: // <<