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compiler: implement full slice expression

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This feature was introduced in Go 1.2 and is used by some standard
library packages.
This commit is contained in:
Ayke van Laethem
2019-08-02 12:19:23 +02:00
committed by Ron Evans
parent 54169c714f
commit 4688664b41
3 changed files with 75 additions and 16 deletions
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compiler/asserts.go
+15 -3
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@@ -56,7 +56,7 @@ func (c *Compiler) emitLookupBoundsCheck(frame *Frame, arrayLen, index llvm.Valu
// normal meaning) and for creating a new slice, where 'capacity' means the
// biggest possible slice capacity, 'low' means len and 'high' means cap. The
// logic is the same in both cases.
func (c *Compiler) emitSliceBoundsCheck(frame *Frame, capacity, low, high llvm.Value, lowType, highType *types.Basic) {
func (c *Compiler) emitSliceBoundsCheck(frame *Frame, capacity, low, high, max llvm.Value, lowType, highType, maxType *types.Basic) {
if frame.fn.IsNoBounds() {
// The //go:nobounds pragma was added to the function to avoid bounds
// checking.
@@ -71,6 +71,9 @@ func (c *Compiler) emitSliceBoundsCheck(frame *Frame, capacity, low, high llvm.V
if high.Type().IntTypeWidth() > capacityType.IntTypeWidth() {
capacityType = high.Type()
}
if max.Type().IntTypeWidth() > capacityType.IntTypeWidth() {
capacityType = max.Type()
}
if capacityType != capacity.Type() {
capacity = c.builder.CreateZExt(capacity, capacityType, "")
}
@@ -90,6 +93,13 @@ func (c *Compiler) emitSliceBoundsCheck(frame *Frame, capacity, low, high llvm.V
high = c.builder.CreateSExt(high, capacityType, "")
}
}
if max.Type().IntTypeWidth() < capacityType.IntTypeWidth() {
if maxType.Info()&types.IsUnsigned != 0 {
max = c.builder.CreateZExt(max, capacityType, "")
} else {
max = c.builder.CreateSExt(max, capacityType, "")
}
}
faultBlock := c.ctx.AddBasicBlock(frame.fn.LLVMFn, "slice.outofbounds")
nextBlock := c.ctx.AddBasicBlock(frame.fn.LLVMFn, "slice.next")
@@ -97,8 +107,10 @@ func (c *Compiler) emitSliceBoundsCheck(frame *Frame, capacity, low, high llvm.V
// Now do the bounds check: low > high || high > capacity
outOfBounds1 := c.builder.CreateICmp(llvm.IntUGT, low, high, "slice.lowhigh")
outOfBounds2 := c.builder.CreateICmp(llvm.IntUGT, high, capacity, "slice.highcap")
outOfBounds := c.builder.CreateOr(outOfBounds1, outOfBounds2, "slice.outofbounds")
outOfBounds2 := c.builder.CreateICmp(llvm.IntUGT, high, max, "slice.highmax")
outOfBounds3 := c.builder.CreateICmp(llvm.IntUGT, max, capacity, "slice.maxcap")
outOfBounds := c.builder.CreateOr(outOfBounds1, outOfBounds2, "slice.lowmax")
outOfBounds = c.builder.CreateOr(outOfBounds, outOfBounds3, "slice.lowcap")
c.builder.CreateCondBr(outOfBounds, faultBlock, nextBlock)
// Fail: this is a nil pointer, exit with a panic.