[dev.simd] cmd/compile: widen index for simd intrinsics jumptable

Feeding an unconverted uint8 to the jumptable can cause
problems either in constant propagation or later at runtime,
depending on details of the input code.

Change-Id: I5fa2299a77a73172349a165f773cf9d1198212bc
Reviewed-on: https://go-review.googlesource.com/c/go/+/702755
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>

diff --git a/src/cmd/compile/internal/ssagen/intrinsics.go b/src/cmd/compile/internal/ssagen/intrinsics.go
index 95da078bba7ef622b1b510084c0b61d5b1f6ad47..ce9a76f6b848f6f43ecb8c6c871551c75fecc99b 100644 (file)
--- a/src/cmd/compile/internal/ssagen/intrinsics.go
+++ b/src/cmd/compile/internal/ssagen/intrinsics.go
@@ -1697,11 +1697,13 @@ func immJumpTable(s *state, idx *ssa.Value, intrinsicCall *ir.CallExpr, genOp fu
        // Make blocks we'll need.
        bEnd := s.f.NewBlock(ssa.BlockPlain)
 
-       t := types.Types[types.TUINT8]
        if !idx.Type.IsKind(types.TUINT8) {
                panic("immJumpTable expects uint8 value")
        }
+
        // We will exhaust 0-255, so no need to check the bounds.
+       t := types.Types[types.TUINTPTR]
+       idx = s.conv(nil, idx, idx.Type, t)
 
        b := s.curBlock
        b.Kind = ssa.BlockJumpTable