[LoongArch] Align stack objects passed to memory intrinsics (#101309)

Memcpy, and other memory intrinsics, typically try to use wider
load/store if the source and destination addresses are aligned. In
CodeGenPrepare, look for calls to memory intrinsics and, if the object
is on the stack, align it to 4-byte (32-bit) or 8-byte (64-bit)
boundaries if it is large enough that we expect memcpy to use wider
load/store instructions to copy it.

Fixes #101295

Author: heiher

llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp

@@ -25,6 +25,7 @@
 #include "llvm/CodeGen/RuntimeLibcallUtil.h"
 #include "llvm/CodeGen/SelectionDAGNodes.h"
 #include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/IntrinsicsLoongArch.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/Debug.h"
@@ -6162,3 +6163,23 @@ bool LoongArchTargetLowering::shouldExtendTypeInLibCall(EVT Type) const {
     return false;
   return true;
 }
+
+// memcpy, and other memory intrinsics, typically tries to use wider load/store
+// if the source/dest is aligned and the copy size is large enough. We therefore
+// want to align such objects passed to memory intrinsics.
+bool LoongArchTargetLowering::shouldAlignPointerArgs(CallInst *CI,
+                                                     unsigned &MinSize,
+                                                     Align &PrefAlign) const {
+  if (!isa<MemIntrinsic>(CI))
+    return false;
+
+  if (Subtarget.is64Bit()) {
+    MinSize = 8;
+    PrefAlign = Align(8);
+  } else {
+    MinSize = 4;
+    PrefAlign = Align(4);
+  }
+
+  return true;
+}

llvm/lib/Target/LoongArch/LoongArchISelLowering.h

@@ -257,6 +257,9 @@ class LoongArchTargetLowering : public TargetLowering {
   bool shouldSignExtendTypeInLibCall(EVT Type, bool IsSigned) const override;
   bool shouldExtendTypeInLibCall(EVT Type) const override;
 
+  bool shouldAlignPointerArgs(CallInst *CI, unsigned &MinSize,
+                              Align &PrefAlign) const override;
+
 private:
   /// Target-specific function used to lower LoongArch calling conventions.
   typedef bool LoongArchCCAssignFn(const DataLayout &DL, LoongArchABI::ABI ABI,

llvm/test/CodeGen/LoongArch/unaligned-memcpy-inline.ll

@@ -103,65 +103,17 @@ define void @t3() {
 ; LA32-NEXT:    .cfi_def_cfa_offset 64
 ; LA32-NEXT:    pcalau12i $a0, %pc_hi20(.L.str)
 ; LA32-NEXT:    addi.w $a0, $a0, %pc_lo12(.L.str)
-; LA32-NEXT:    ld.b $a1, $a0, 21
-; LA32-NEXT:    ld.bu $a2, $a0, 20
-; LA32-NEXT:    slli.w $a1, $a1, 8
-; LA32-NEXT:    or $a1, $a1, $a2
+; LA32-NEXT:    ld.h $a1, $a0, 20
+; LA32-NEXT:    ld.w $a2, $a0, 16
 ; LA32-NEXT:    st.h $a1, $sp, 20
-; LA32-NEXT:    ld.bu $a1, $a0, 17
-; LA32-NEXT:    ld.bu $a2, $a0, 16
-; LA32-NEXT:    ld.bu $a3, $a0, 18
-; LA32-NEXT:    ld.bu $a4, $a0, 19
-; LA32-NEXT:    slli.w $a1, $a1, 8
-; LA32-NEXT:    or $a1, $a1, $a2
-; LA32-NEXT:    slli.w $a2, $a3, 16
-; LA32-NEXT:    slli.w $a3, $a4, 24
-; LA32-NEXT:    or $a2, $a3, $a2
-; LA32-NEXT:    or $a1, $a2, $a1
-; LA32-NEXT:    st.w $a1, $sp, 16
-; LA32-NEXT:    ld.bu $a1, $a0, 13
-; LA32-NEXT:    ld.bu $a2, $a0, 12
-; LA32-NEXT:    ld.bu $a3, $a0, 14
-; LA32-NEXT:    ld.bu $a4, $a0, 15
-; LA32-NEXT:    slli.w $a1, $a1, 8
-; LA32-NEXT:    or $a1, $a1, $a2
-; LA32-NEXT:    slli.w $a2, $a3, 16
-; LA32-NEXT:    slli.w $a3, $a4, 24
-; LA32-NEXT:    or $a2, $a3, $a2
-; LA32-NEXT:    or $a1, $a2, $a1
+; LA32-NEXT:    st.w $a2, $sp, 16
+; LA32-NEXT:    ld.w $a1, $a0, 12
+; LA32-NEXT:    ld.w $a2, $a0, 8
+; LA32-NEXT:    ld.w $a3, $a0, 4
+; LA32-NEXT:    ld.w $a0, $a0, 0
 ; LA32-NEXT:    st.w $a1, $sp, 12
-; LA32-NEXT:    ld.bu $a1, $a0, 9
-; LA32-NEXT:    ld.bu $a2, $a0, 8
-; LA32-NEXT:    ld.bu $a3, $a0, 10
-; LA32-NEXT:    ld.bu $a4, $a0, 11
-; LA32-NEXT:    slli.w $a1, $a1, 8
-; LA32-NEXT:    or $a1, $a1, $a2
-; LA32-NEXT:    slli.w $a2, $a3, 16
-; LA32-NEXT:    slli.w $a3, $a4, 24
-; LA32-NEXT:    or $a2, $a3, $a2
-; LA32-NEXT:    or $a1, $a2, $a1
-; LA32-NEXT:    st.w $a1, $sp, 8
-; LA32-NEXT:    ld.bu $a1, $a0, 5
-; LA32-NEXT:    ld.bu $a2, $a0, 4
-; LA32-NEXT:    ld.bu $a3, $a0, 6
-; LA32-NEXT:    ld.bu $a4, $a0, 7
-; LA32-NEXT:    slli.w $a1, $a1, 8
-; LA32-NEXT:    or $a1, $a1, $a2
-; LA32-NEXT:    slli.w $a2, $a3, 16
-; LA32-NEXT:    slli.w $a3, $a4, 24
-; LA32-NEXT:    or $a2, $a3, $a2
-; LA32-NEXT:    or $a1, $a2, $a1
-; LA32-NEXT:    st.w $a1, $sp, 4
-; LA32-NEXT:    ld.bu $a1, $a0, 1
-; LA32-NEXT:    ld.bu $a2, $a0, 0
-; LA32-NEXT:    ld.bu $a3, $a0, 2
-; LA32-NEXT:    ld.bu $a0, $a0, 3
-; LA32-NEXT:    slli.w $a1, $a1, 8
-; LA32-NEXT:    or $a1, $a1, $a2
-; LA32-NEXT:    slli.w $a2, $a3, 16
-; LA32-NEXT:    slli.w $a0, $a0, 24
-; LA32-NEXT:    or $a0, $a0, $a2
-; LA32-NEXT:    or $a0, $a0, $a1
+; LA32-NEXT:    st.w $a2, $sp, 8
+; LA32-NEXT:    st.w $a3, $sp, 4
 ; LA32-NEXT:    st.w $a0, $sp, 0
 ; LA32-NEXT:    addi.w $sp, $sp, 64
 ; LA32-NEXT:    ret
@@ -172,67 +124,13 @@ define void @t3() {
 ; LA64-NEXT:    .cfi_def_cfa_offset 64
 ; LA64-NEXT:    pcalau12i $a0, %pc_hi20(.L.str)
 ; LA64-NEXT:    addi.d $a0, $a0, %pc_lo12(.L.str)
-; LA64-NEXT:    ld.b $a1, $a0, 21
-; LA64-NEXT:    ld.bu $a2, $a0, 20
-; LA64-NEXT:    slli.d $a1, $a1, 8
-; LA64-NEXT:    or $a1, $a1, $a2
+; LA64-NEXT:    ld.h $a1, $a0, 20
+; LA64-NEXT:    ld.w $a2, $a0, 16
+; LA64-NEXT:    ld.d $a3, $a0, 8
+; LA64-NEXT:    ld.d $a0, $a0, 0
 ; LA64-NEXT:    st.h $a1, $sp, 20
-; LA64-NEXT:    ld.bu $a1, $a0, 17
-; LA64-NEXT:    ld.bu $a2, $a0, 16
-; LA64-NEXT:    ld.bu $a3, $a0, 18
-; LA64-NEXT:    ld.b $a4, $a0, 19
-; LA64-NEXT:    slli.d $a1, $a1, 8
-; LA64-NEXT:    or $a1, $a1, $a2
-; LA64-NEXT:    slli.d $a2, $a3, 16
-; LA64-NEXT:    slli.d $a3, $a4, 24
-; LA64-NEXT:    or $a2, $a3, $a2
-; LA64-NEXT:    or $a1, $a2, $a1
-; LA64-NEXT:    st.w $a1, $sp, 16
-; LA64-NEXT:    ld.bu $a1, $a0, 9
-; LA64-NEXT:    ld.bu $a2, $a0, 8
-; LA64-NEXT:    ld.bu $a3, $a0, 10
-; LA64-NEXT:    ld.bu $a4, $a0, 11
-; LA64-NEXT:    slli.d $a1, $a1, 8
-; LA64-NEXT:    or $a1, $a1, $a2
-; LA64-NEXT:    slli.d $a2, $a3, 16
-; LA64-NEXT:    slli.d $a3, $a4, 24
-; LA64-NEXT:    or $a2, $a3, $a2
-; LA64-NEXT:    or $a1, $a2, $a1
-; LA64-NEXT:    ld.bu $a2, $a0, 13
-; LA64-NEXT:    ld.bu $a3, $a0, 12
-; LA64-NEXT:    ld.bu $a4, $a0, 14
-; LA64-NEXT:    ld.bu $a5, $a0, 15
-; LA64-NEXT:    slli.d $a2, $a2, 8
-; LA64-NEXT:    or $a2, $a2, $a3
-; LA64-NEXT:    slli.d $a3, $a4, 16
-; LA64-NEXT:    slli.d $a4, $a5, 24
-; LA64-NEXT:    or $a3, $a4, $a3
-; LA64-NEXT:    or $a2, $a3, $a2
-; LA64-NEXT:    slli.d $a2, $a2, 32
-; LA64-NEXT:    or $a1, $a2, $a1
-; LA64-NEXT:    st.d $a1, $sp, 8
-; LA64-NEXT:    ld.bu $a1, $a0, 1
-; LA64-NEXT:    ld.bu $a2, $a0, 0
-; LA64-NEXT:    ld.bu $a3, $a0, 2
-; LA64-NEXT:    ld.bu $a4, $a0, 3
-; LA64-NEXT:    slli.d $a1, $a1, 8
-; LA64-NEXT:    or $a1, $a1, $a2
-; LA64-NEXT:    slli.d $a2, $a3, 16
-; LA64-NEXT:    slli.d $a3, $a4, 24
-; LA64-NEXT:    or $a2, $a3, $a2
-; LA64-NEXT:    or $a1, $a2, $a1
-; LA64-NEXT:    ld.bu $a2, $a0, 5
-; LA64-NEXT:    ld.bu $a3, $a0, 4
-; LA64-NEXT:    ld.bu $a4, $a0, 6
-; LA64-NEXT:    ld.bu $a0, $a0, 7
-; LA64-NEXT:    slli.d $a2, $a2, 8
-; LA64-NEXT:    or $a2, $a2, $a3
-; LA64-NEXT:    slli.d $a3, $a4, 16
-; LA64-NEXT:    slli.d $a0, $a0, 24
-; LA64-NEXT:    or $a0, $a0, $a3
-; LA64-NEXT:    or $a0, $a0, $a2
-; LA64-NEXT:    slli.d $a0, $a0, 32
-; LA64-NEXT:    or $a0, $a0, $a1
+; LA64-NEXT:    st.w $a2, $sp, 16
+; LA64-NEXT:    st.d $a3, $sp, 8
 ; LA64-NEXT:    st.d $a0, $sp, 0
 ; LA64-NEXT:    addi.d $sp, $sp, 64
 ; LA64-NEXT:    ret