[llvm] [RISCV] Mask integer and float loads as canFoldAsLoad for stackmaps (PR #165761)
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Thu Oct 30 11:24:16 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-risc-v
Author: Philip Reames (preames)
<details>
<summary>Changes</summary>
We have two mechanisms used in inline spilled for folding a load into a consuming instruction. One is used for stack reloads, the other for other load instructions (usually argument loads). We currently only implement optimizations for the first case, but stackmaps have generic support in target independent code for the other. We can go ahead and set the flag to enable that optimization.
The primary motivation for this is that if we enable load rematerialization without it, we run into crashes where we can't make progress through rematerialization.
We probably should enable the other foldMemoryOperand hook for RISCV specific instructions, but that's separate optimization.
---
Full diff: https://github.com/llvm/llvm-project/pull/165761.diff
5 Files Affected:
- (modified) llvm/lib/Target/RISCV/RISCVInstrInfo.cpp (+1-1)
- (modified) llvm/lib/Target/RISCV/RISCVInstrInfo.td (+3-1)
- (modified) llvm/lib/Target/RISCV/RISCVInstrInfoD.td (+1)
- (modified) llvm/lib/Target/RISCV/RISCVInstrInfoF.td (+1)
- (modified) llvm/test/CodeGen/RISCV/rv64-stackmap.ll (+4-4)
``````````diff
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
index 912b82d294f44..069f2b0c1e885 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
@@ -869,7 +869,7 @@ std::optional<unsigned> getFoldedOpcode(MachineFunction &MF, MachineInstr &MI,
}
}
-// This is the version used during inline spilling
+// This is the version used during InlineSpiller::spillAroundUses
MachineInstr *RISCVInstrInfo::foldMemoryOperandImpl(
MachineFunction &MF, MachineInstr &MI, ArrayRef<unsigned> Ops,
MachineBasicBlock::iterator InsertPt, int FrameIndex, LiveIntervals *LIS,
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.td b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
index 7c89686ebfb3c..9cb53fb27a2d2 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfo.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
@@ -768,7 +768,7 @@ def BGE : BranchCC_rri<0b101, "bge">;
def BLTU : BranchCC_rri<0b110, "bltu">;
def BGEU : BranchCC_rri<0b111, "bgeu">;
-let IsSignExtendingOpW = 1 in {
+let IsSignExtendingOpW = 1, canFoldAsLoad = 1 in {
def LB : Load_ri<0b000, "lb">, Sched<[WriteLDB, ReadMemBase]>;
def LH : Load_ri<0b001, "lh">, Sched<[WriteLDH, ReadMemBase]>;
def LW : Load_ri<0b010, "lw">, Sched<[WriteLDW, ReadMemBase]>;
@@ -889,8 +889,10 @@ def CSRRCI : CSR_ii<0b111, "csrrci">;
/// RV64I instructions
let Predicates = [IsRV64] in {
+let canFoldAsLoad = 1 in {
def LWU : Load_ri<0b110, "lwu">, Sched<[WriteLDW, ReadMemBase]>;
def LD : Load_ri<0b011, "ld">, Sched<[WriteLDD, ReadMemBase]>;
+}
def SD : Store_rri<0b011, "sd">, Sched<[WriteSTD, ReadStoreData, ReadMemBase]>;
let IsSignExtendingOpW = 1 in {
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoD.td b/llvm/lib/Target/RISCV/RISCVInstrInfoD.td
index afac37d6337d4..4ffe3e62ac501 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfoD.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfoD.td
@@ -71,6 +71,7 @@ defvar DExtsRV64 = [DExt, ZdinxExt];
//===----------------------------------------------------------------------===//
let Predicates = [HasStdExtD] in {
+let canFoldAsLoad = 1 in
def FLD : FPLoad_r<0b011, "fld", FPR64, WriteFLD64>;
// Operands for stores are in the order srcreg, base, offset rather than
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoF.td b/llvm/lib/Target/RISCV/RISCVInstrInfoF.td
index 6571d998246a7..b30f8ec820c15 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfoF.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfoF.td
@@ -330,6 +330,7 @@ class PseudoFROUND<DAGOperand Ty, ValueType vt, ValueType intvt = XLenVT>
//===----------------------------------------------------------------------===//
let Predicates = [HasStdExtF] in {
+let canFoldAsLoad = 1 in
def FLW : FPLoad_r<0b010, "flw", FPR32, WriteFLD32>;
// Operands for stores are in the order srcreg, base, offset rather than
diff --git a/llvm/test/CodeGen/RISCV/rv64-stackmap.ll b/llvm/test/CodeGen/RISCV/rv64-stackmap.ll
index c3183a1a3e036..9aefa90684dd3 100644
--- a/llvm/test/CodeGen/RISCV/rv64-stackmap.ll
+++ b/llvm/test/CodeGen/RISCV/rv64-stackmap.ll
@@ -38,8 +38,8 @@
; CHECK-NEXT: .quad liveConstant
; CHECK-NEXT: .quad 0
; CHECK-NEXT: .quad 1
-; CHECK-NEXT: .quad spilledValue
-; CHECK-NEXT: .quad 144
+; CHECK-NEXT: .quad liveArgs
+; CHECK-NEXT: .quad 0
; CHECK-NEXT: .quad 1
; CHECK-NEXT: .quad directFrameIdx
; CHECK-NEXT: .quad 48
@@ -278,7 +278,7 @@ define void @liveConstant() {
;
; Verify 28 stack map entries.
;
-; CHECK-LABEL: .word .L{{.*}}-spilledValue
+; CHECK-LABEL: .word .L{{.*}}-liveArgs
; CHECK-NEXT: .half 0
; CHECK-NEXT: .half 28
;
@@ -290,7 +290,7 @@ define void @liveConstant() {
; CHECK-NEXT: .half 2
; CHECK-NEXT: .half 0
; CHECK-NEXT: .word
-define void @spilledValue(i64 %arg0, i64 %arg1, i64 %arg2, i64 %arg3, i64 %arg4, i64 %l0, i64 %l1, i64 %l2, i64 %l3, i64 %l4, i64 %l5, i64 %l6, i64 %l7, i64 %l8, i64 %l9, i64 %l10, i64 %l11, i64 %l12, i64 %l13, i64 %l14, i64 %l15, i64 %l16, i64 %l17, i64 %l18, i64 %l19, i64 %l20, i64 %l21, i64 %l22, i64 %l23, i64 %l24, i8 %l25, i16 zeroext %l26, i32 signext %l27) {
+define void @liveArgs(i64 %arg0, i64 %arg1, i64 %arg2, i64 %arg3, i64 %arg4, i64 %l0, i64 %l1, i64 %l2, i64 %l3, i64 %l4, i64 %l5, i64 %l6, i64 %l7, i64 %l8, i64 %l9, i64 %l10, i64 %l11, i64 %l12, i64 %l13, i64 %l14, i64 %l15, i64 %l16, i64 %l17, i64 %l18, i64 %l19, i64 %l20, i64 %l21, i64 %l22, i64 %l23, i64 %l24, i8 %l25, i16 zeroext %l26, i32 signext %l27) {
entry:
call void (i64, i32, ptr, i32, ...) @llvm.experimental.patchpoint.void(i64 11, i32 28, ptr null, i32 5, i64 %arg0, i64 %arg1, i64 %arg2, i64 %arg3, i64 %arg4, i64 %l0, i64 %l1, i64 %l2, i64 %l3, i64 %l4, i64 %l5, i64 %l6, i64 %l7, i64 %l8, i64 %l9, i64 %l10, i64 %l11, i64 %l12, i64 %l13, i64 %l14, i64 %l15, i64 %l16, i64 %l17, i64 %l18, i64 %l19, i64 %l20, i64 %l21, i64 %l22, i64 %l23, i64 %l24, i8 %l25, i16 %l26, i32 %l27)
ret void
``````````
</details>
https://github.com/llvm/llvm-project/pull/165761
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