[llvm] r190636 - Fix PPC ABI for ByVal structs with vector members
David Blaikie
dblaikie at gmail.com
Thu Feb 19 13:57:13 PST 2015
On Thu, Sep 12, 2013 at 4:20 PM, Hal Finkel <hfinkel at anl.gov> wrote:
> Author: hfinkel
> Date: Thu Sep 12 18:20:06 2013
> New Revision: 190636
>
> URL: http://llvm.org/viewvc/llvm-project?rev=190636&view=rev
> Log:
> Fix PPC ABI for ByVal structs with vector members
>
> When a structure is passed by value, and that structure contains a vector
> member, according to the PPC ABI, the structure will receive enhanced
> alignment
> (so that the vector within the structure will always be aligned).
>
> This should resolve PR16641.
>
In an effort to simplify byval in a future world of opaque (untyped)
pointers, I was considering changing "%struct.foo byval" to "ptr
byval(num_bytes)" - which I think would work for every target except PPC
(PPC, and the code in this commit, is the only case I could find of
overriding getByValTypeAlignment that wasn't just the default of asking
DataLayout for the type's alignment).
Is this code necessary? If I remove the entire PPCTargetLowering override
of getByValTypeAlignment this test case (& everything else in check-llvm)
appears to still pass.
> Added:
> llvm/trunk/test/CodeGen/PowerPC/vec-abi-align.ll
> Modified:
> llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp
>
> Modified: llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp?rev=190636&r1=190635&r2=190636&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp (original)
> +++ llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp Thu Sep 12 18:20:06
> 2013
> @@ -578,24 +578,48 @@ PPCTargetLowering::PPCTargetLowering(PPC
> }
> }
>
> +/// getMaxByValAlign - Helper for getByValTypeAlignment to determine
> +/// the desired ByVal argument alignment.
> +static void getMaxByValAlign(Type *Ty, unsigned &MaxAlign,
> + unsigned MaxMaxAlign) {
> + if (MaxAlign == MaxMaxAlign)
> + return;
> + if (VectorType *VTy = dyn_cast<VectorType>(Ty)) {
> + if (MaxMaxAlign >= 32 && VTy->getBitWidth() >= 256)
> + MaxAlign = 32;
> + else if (VTy->getBitWidth() >= 128 && MaxAlign < 16)
> + MaxAlign = 16;
> + } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
> + unsigned EltAlign = 0;
> + getMaxByValAlign(ATy->getElementType(), EltAlign, MaxMaxAlign);
> + if (EltAlign > MaxAlign)
> + MaxAlign = EltAlign;
> + } else if (StructType *STy = dyn_cast<StructType>(Ty)) {
> + for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
> + unsigned EltAlign = 0;
> + getMaxByValAlign(STy->getElementType(i), EltAlign, MaxMaxAlign);
> + if (EltAlign > MaxAlign)
> + MaxAlign = EltAlign;
> + if (MaxAlign == MaxMaxAlign)
> + break;
> + }
> + }
> +}
> +
> /// getByValTypeAlignment - Return the desired alignment for ByVal
> aggregate
> /// function arguments in the caller parameter area.
> unsigned PPCTargetLowering::getByValTypeAlignment(Type *Ty) const {
> const TargetMachine &TM = getTargetMachine();
> // Darwin passes everything on 4 byte boundary.
> - if (TM.getSubtarget<PPCSubtarget>().isDarwin())
> + if (PPCSubTarget.isDarwin())
> return 4;
>
> // 16byte and wider vectors are passed on 16byte boundary.
> - if (VectorType *VTy = dyn_cast<VectorType>(Ty))
> - if (VTy->getBitWidth() >= 128)
> - return 16;
> -
> // The rest is 8 on PPC64 and 4 on PPC32 boundary.
> - if (PPCSubTarget.isPPC64())
> - return 8;
> -
> - return 4;
> + unsigned Align = PPCSubTarget.isPPC64() ? 8 : 4;
> + if (PPCSubTarget.hasAltivec() || PPCSubTarget.hasQPX())
> + getMaxByValAlign(Ty, Align, PPCSubTarget.hasQPX() ? 32 : 16);
> + return Align;
> }
>
> const char *PPCTargetLowering::getTargetNodeName(unsigned Opcode) const {
> @@ -2281,6 +2305,13 @@ PPCTargetLowering::LowerFormalArguments_
> InVals.push_back(FIN);
> continue;
> }
> +
> + unsigned BVAlign = Flags.getByValAlign();
> + if (BVAlign > 8) {
> + ArgOffset = ((ArgOffset+BVAlign-1)/BVAlign)*BVAlign;
> + CurArgOffset = ArgOffset;
> + }
> +
> // All aggregates smaller than 8 bytes must be passed
> right-justified.
> if (ObjSize < PtrByteSize)
> CurArgOffset = CurArgOffset + (PtrByteSize - ObjSize);
> @@ -3870,6 +3901,15 @@ PPCTargetLowering::LowerCall_64SVR4(SDVa
> if (Size == 0)
> continue;
>
> + unsigned BVAlign = Flags.getByValAlign();
> + if (BVAlign > 8) {
> + if (BVAlign % PtrByteSize != 0)
> + llvm_unreachable(
> + "ByVal alignment is not a multiple of the pointer size");
> +
> + ArgOffset = ((ArgOffset+BVAlign-1)/BVAlign)*BVAlign;
> + }
> +
> // All aggregates smaller than 8 bytes must be passed
> right-justified.
> if (Size==1 || Size==2 || Size==4) {
> EVT VT = (Size==1) ? MVT::i8 : ((Size==2) ? MVT::i16 : MVT::i32);
>
> Added: llvm/trunk/test/CodeGen/PowerPC/vec-abi-align.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/vec-abi-align.ll?rev=190636&view=auto
>
> ==============================================================================
> --- llvm/trunk/test/CodeGen/PowerPC/vec-abi-align.ll (added)
> +++ llvm/trunk/test/CodeGen/PowerPC/vec-abi-align.ll Thu Sep 12 18:20:06
> 2013
> @@ -0,0 +1,64 @@
> +; RUN: llc -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 < %s |
> FileCheck %s
> +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-f128:128:128-v128:128:128-n32:64"
> +target triple = "powerpc64-unknown-linux-gnu"
> +
> +%struct.s2 = type { i64, <4 x float> }
> +
> + at ve = external global <4 x float>
> + at n = external global i64
> +
> +; Function Attrs: nounwind
> +define void @test1(i64 %d1, i64 %d2, i64 %d3, i64 %d4, i64 %d5, i64 %d6,
> i64 %d7, i64 %d8, i64 %d9, <4 x float> inreg %vs.coerce) #0 {
> +entry:
> + store <4 x float> %vs.coerce, <4 x float>* @ve, align 16, !tbaa !0
> + ret void
> +
> +; CHECK-LABEL: @test1
> +; CHECK: stvx 2,
> +; CHECK: blr
> +}
> +
> +; Function Attrs: nounwind
> +define void @test2(i64 %d1, i64 %d2, i64 %d3, i64 %d4, i64 %d5, i64 %d6,
> i64 %d7, i64 %d8, %struct.s2* byval nocapture readonly %vs) #0 {
> +entry:
> + %m = getelementptr inbounds %struct.s2* %vs, i64 0, i32 0
> + %0 = load i64* %m, align 8, !tbaa !2
> + store i64 %0, i64* @n, align 8, !tbaa !2
> + %v = getelementptr inbounds %struct.s2* %vs, i64 0, i32 1
> + %1 = load <4 x float>* %v, align 16, !tbaa !0
> + store <4 x float> %1, <4 x float>* @ve, align 16, !tbaa !0
> + ret void
> +
> +; CHECK-LABEL: @test2
> +; CHECK: ld {{[0-9]+}}, 112(1)
> +; CHECK: li [[REG16:[0-9]+]], 16
> +; CHECK: addi [[REGB:[0-9]+]], 1, 112
> +; CHECK: lvx 2, [[REGB]], [[REG16]]
> +; CHECK: blr
> +}
> +
> +; Function Attrs: nounwind
> +define void @test3(i64 %d1, i64 %d2, i64 %d3, i64 %d4, i64 %d5, i64 %d6,
> i64 %d7, i64 %d8, i64 %d9, %struct.s2* byval nocapture readonly %vs) #0 {
> +entry:
> + %m = getelementptr inbounds %struct.s2* %vs, i64 0, i32 0
> + %0 = load i64* %m, align 8, !tbaa !2
> + store i64 %0, i64* @n, align 8, !tbaa !2
> + %v = getelementptr inbounds %struct.s2* %vs, i64 0, i32 1
> + %1 = load <4 x float>* %v, align 16, !tbaa !0
> + store <4 x float> %1, <4 x float>* @ve, align 16, !tbaa !0
> + ret void
> +
> +; CHECK-LABEL: @test3
> +; CHECK: ld {{[0-9]+}}, 128(1)
> +; CHECK: li [[REG16:[0-9]+]], 16
> +; CHECK: addi [[REGB:[0-9]+]], 1, 128
> +; CHECK: lvx 2, [[REGB]], [[REG16]]
> +; CHECK: blr
> +}
> +
> +attributes #0 = { nounwind }
> +
> +!0 = metadata !{metadata !"omnipotent char", metadata !1}
> +!1 = metadata !{metadata !"Simple C/C++ TBAA"}
> +!2 = metadata !{metadata !"long", metadata !0}
> +
>
>
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