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b806d02b5b
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
19 lines
641 B
LLVM
19 lines
641 B
LLVM
; RUN: llc -mcpu=ppc64 -O0 -fast-isel=false < %s | FileCheck %s
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; Checks for a previous bug where vspltisb/vaddubm were issued in place
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; of vsplitsh/vadduhm.
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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"
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target triple = "powerpc64-unknown-linux-gnu"
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@a = external global <16 x i8>
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define void @foo() nounwind ssp {
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; CHECK: foo:
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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
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; CHECK: vspltish [[REG:[0-9]+]], 8
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; CHECK: vadduhm {{[0-9]+}}, [[REG]], [[REG]]
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ret void
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}
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