[SVE] Ensure SVE call operands passed via memory are correctly initialised. (#66070)

The stores created when passing operands via memory don't typically
maintain the chain, because they can be done in any order. Instead,
a new chain is created based on all collated stores. SVE parameters
passed via memory don't follow this idiom and try to maintain the
chain, which unfortunately can result in them being incorrectly
deadcoded when the chain is recreated.

This patch brings the SVE side in line with the non-SVE side to
ensure no stores become lost whilst also allowing greater flexibility
when ordering the stores.

Author: paulwalker-arm

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -7388,7 +7388,9 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
       // Ensure we generate all stores for each tuple part, whilst updating the
       // pointer after each store correctly using vscale.
       while (NumParts) {
-        Chain = DAG.getStore(Chain, DL, OutVals[i], Ptr, MPI);
+        SDValue Store = DAG.getStore(Chain, DL, OutVals[i], Ptr, MPI);
+        MemOpChains.push_back(Store);
+
         NumParts--;
         if (NumParts > 0) {
           SDValue BytesIncrement;

llvm/test/CodeGen/AArch64/arm64ec-varargs.ll

@@ -35,15 +35,15 @@ define void @varargs_caller() nounwind {
 ; CHECK-NEXT:    sub sp, sp, #48
 ; CHECK-NEXT:    mov x4, sp
 ; CHECK-NEXT:    add x8, sp, #16
-; CHECK-NEXT:    mov x9, #4617315517961601024
-; CHECK-NEXT:    mov x0, #4607182418800017408
-; CHECK-NEXT:    mov w1, #2
-; CHECK-NEXT:    mov x2, #4613937818241073152
-; CHECK-NEXT:    mov w3, #4
-; CHECK-NEXT:    mov w5, #16
+; CHECK-NEXT:    mov x9, #4617315517961601024 // =0x4014000000000000
+; CHECK-NEXT:    mov x0, #4607182418800017408 // =0x3ff0000000000000
+; CHECK-NEXT:    mov w1, #2 // =0x2
+; CHECK-NEXT:    mov x2, #4613937818241073152 // =0x4008000000000000
+; CHECK-NEXT:    mov w3, #4 // =0x4
+; CHECK-NEXT:    mov w5, #16 // =0x10
 ; CHECK-NEXT:    stp xzr, x30, [sp, #24] // 8-byte Folded Spill
-; CHECK-NEXT:    stp x8, xzr, [sp, #8]
-; CHECK-NEXT:    str x9, [sp]
+; CHECK-NEXT:    stp x9, x8, [sp]
+; CHECK-NEXT:    str xzr, [sp, #16]
 ; CHECK-NEXT:    bl varargs_callee
 ; CHECK-NEXT:    ldr x30, [sp, #32] // 8-byte Folded Reload
 ; CHECK-NEXT:    add sp, sp, #48
@@ -71,16 +71,16 @@ define void @varargs_many_argscalleer() nounwind {
 ; CHECK-NEXT:    sub sp, sp, #64
 ; CHECK-NEXT:    movi v0.2d, #0000000000000000
 ; CHECK-NEXT:    mov x4, sp
-; CHECK-NEXT:    mov x8, #4618441417868443648
+; CHECK-NEXT:    mov x8, #4618441417868443648 // =0x4018000000000000
 ; CHECK-NEXT:    add x9, sp, #16
 ; CHECK-NEXT:    add x3, sp, #32
-; CHECK-NEXT:    mov x0, #4607182418800017408
-; CHECK-NEXT:    mov x1, #4611686018427387904
-; CHECK-NEXT:    mov x2, #4613937818241073152
-; CHECK-NEXT:    mov w5, #16
+; CHECK-NEXT:    mov x0, #4607182418800017408 // =0x3ff0000000000000
+; CHECK-NEXT:    mov x1, #4611686018427387904 // =0x4000000000000000
+; CHECK-NEXT:    mov x2, #4613937818241073152 // =0x4008000000000000
+; CHECK-NEXT:    mov w5, #16 // =0x10
 ; CHECK-NEXT:    str x30, [sp, #48] // 8-byte Folded Spill
-; CHECK-NEXT:    stp q0, q0, [sp, #16]
 ; CHECK-NEXT:    stp x9, x8, [sp]
+; CHECK-NEXT:    stp q0, q0, [sp, #16]
 ; CHECK-NEXT:    bl varargs_many_argscallee
 ; CHECK-NEXT:    ldr x30, [sp, #48] // 8-byte Folded Reload
 ; CHECK-NEXT:    add sp, sp, #64

llvm/test/CodeGen/AArch64/sve-calling-convention-mixed.ll

@@ -18,10 +18,10 @@ define float @foo1(ptr %x0, ptr %x1, ptr %x2) nounwind {
 ; CHECK-NEXT:    ld1d { z5.d }, p0/z, [x2]
 ; CHECK-NEXT:    mov x0, sp
 ; CHECK-NEXT:    ptrue p0.d
-; CHECK-NEXT:    st1d { z16.d }, p0, [sp]
-; CHECK-NEXT:    st1d { z17.d }, p0, [sp, #1, mul vl]
-; CHECK-NEXT:    st1d { z18.d }, p0, [sp, #2, mul vl]
 ; CHECK-NEXT:    st1d { z19.d }, p0, [sp, #3, mul vl]
+; CHECK-NEXT:    st1d { z18.d }, p0, [sp, #2, mul vl]
+; CHECK-NEXT:    st1d { z17.d }, p0, [sp, #1, mul vl]
+; CHECK-NEXT:    st1d { z16.d }, p0, [sp]
 ; CHECK-NEXT:    bl callee1
 ; CHECK-NEXT:    addvl sp, sp, #4
 ; CHECK-NEXT:    ldp x29, x30, [sp], #16 // 16-byte Folded Reload
@@ -73,10 +73,10 @@ define float @foo2(ptr %x0, ptr %x1) nounwind {
 ; CHECK-NEXT:    mov w7, #7 // =0x7
 ; CHECK-NEXT:    add x9, sp, #16
 ; CHECK-NEXT:    ptrue p0.d
-; CHECK-NEXT:    st1d { z16.d }, p0, [x9]
-; CHECK-NEXT:    st1d { z17.d }, p0, [x9, #1, mul vl]
-; CHECK-NEXT:    st1d { z18.d }, p0, [x9, #2, mul vl]
 ; CHECK-NEXT:    st1d { z19.d }, p0, [x9, #3, mul vl]
+; CHECK-NEXT:    st1d { z18.d }, p0, [x9, #2, mul vl]
+; CHECK-NEXT:    st1d { z17.d }, p0, [x9, #1, mul vl]
+; CHECK-NEXT:    st1d { z16.d }, p0, [x9]
 ; CHECK-NEXT:    str x8, [sp]
 ; CHECK-NEXT:    bl callee2
 ; CHECK-NEXT:    addvl sp, sp, #4
@@ -121,9 +121,9 @@ define float @foo3(ptr %x0, ptr %x1, ptr %x2) nounwind {
 ; CHECK-NEXT:    fmov s1, #2.00000000
 ; CHECK-NEXT:    mov x0, sp
 ; CHECK-NEXT:    ptrue p0.d
-; CHECK-NEXT:    st1d { z16.d }, p0, [sp]
-; CHECK-NEXT:    st1d { z17.d }, p0, [sp, #1, mul vl]
 ; CHECK-NEXT:    st1d { z18.d }, p0, [sp, #2, mul vl]
+; CHECK-NEXT:    st1d { z17.d }, p0, [sp, #1, mul vl]
+; CHECK-NEXT:    st1d { z16.d }, p0, [sp]
 ; CHECK-NEXT:    bl callee3
 ; CHECK-NEXT:    addvl sp, sp, #3
 ; CHECK-NEXT:    ldp x29, x30, [sp], #16 // 16-byte Folded Reload
@@ -714,6 +714,10 @@ define void @verify_all_operands_are_initialised() {
 ; CHECK-NEXT:    fmov s6, #6.00000000
 ; CHECK-NEXT:    fmov s7, #7.00000000
 ; CHECK-NEXT:    add x0, sp, #16
+; CHECK-NEXT:    add x9, sp, #16
+; CHECK-NEXT:    ptrue p0.s
+; CHECK-NEXT:    fmov z16.s, #9.00000000
+; CHECK-NEXT:    st1w { z16.s }, p0, [x9]
 ; CHECK-NEXT:    str w8, [sp]
 ; CHECK-NEXT:    bl func_f8_and_v0_passed_via_memory
 ; CHECK-NEXT:    addvl sp, sp, #1