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llvm-project/llvm/test/CodeGen/PowerPC/splat-bug.ll

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[PATCH] Correct type used for VADD_SPLAT optimization on PowerPC In PPCISelLowering.cpp: PPCTargetLowering::LowerBUILD_VECTOR(), there is an optimization for certain patterns to generate one or two vector splats followed by a vector add or subtract. This operation is represented by a VADD_SPLAT in the selection DAG. Prior to this patch, it was possible for the VADD_SPLAT to be assigned the wrong data type, causing incorrect code generation. This patch corrects the problem. Specifically, the code previously assigned the value type of the BUILD_VECTOR node to the newly generated VADD_SPLAT node. This is correct much of the time, but not always. The problem is that the call to isConstantSplat() may return a SplatBitSize that is not the same as the number of bits in the original element vector type. The correct type to assign is a vector type with the same element bit size as SplatBitSize. The included test case shows an example of this, where the BUILD_VECTOR node has a type of v16i8. The vector to be built is {0, 16, 0, 16, 0, 16, 0, 16, 0, 16, 0, 16, 0, 16, 0, 16}. isConstantSplat detects that we can generate a splat of 16 for type v8i16, which is the type we must assign to the VADD_SPLAT node. If we do not, we generate a vspltisb of 8 and a vaddubm, which generates the incorrect result {16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16}. The correct code generation is a vspltish of 8 and a vadduhm. This patch also corrected code generation for CodeGen/PowerPC/2008-07-10-SplatMiscompile.ll, which had been marked as an XFAIL, so we can remove the XFAIL from the test case. llvm-svn: 209662
2014-05-27 23:57:51 +08:00
; RUN: llc -mcpu=ppc64 -O0 -fast-isel=false < %s | FileCheck %s
; Checks for a previous bug where vspltisb/vaddubm were issued in place
; of vsplitsh/vadduhm.
target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v128:128:128-n32:64"
target triple = "powerpc64-unknown-linux-gnu"
@a = external global <16 x i8>
define void @foo() nounwind ssp {
; CHECK: foo:
store <16 x i8> <i8 0, i8 16, i8 0, i8 16, i8 0, i8 16, i8 0, i8 16, i8 0, i8 16, i8 0, i8 16, i8 0, i8 16, i8 0, i8 16>, <16 x i8>* @a
; CHECK: vspltish [[REG:[0-9]+]], 8
; CHECK: vadduhm {{[0-9]+}}, [[REG]], [[REG]]
ret void
}