[llvm] [RISCV] Enable rematerialization for scalar loads (PR #166774)
Luke Lau via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 17 22:58:02 PST 2025
================
@@ -200,3 +200,168 @@ for.end: ; preds = %for.inc, %entry
}
declare i32 @foo(i32, i32, i32, i32, i32, i32)
+
+define void @remat_load(i32 %0, i32 %1, i32 %2, i32 %3, i32 %4, i32 %5, i32 %6, i32 %7, double %8, double %9, double %10, double %11, double %12, double %13, double %14, double %15, i8 %stackarg0, i16 %stackarg1, i32 %stackarg2, i64 %stackarg3, half %stackarg4, bfloat %stackarg5, float %stackarg6, double %stackarg7, ptr %p) nounwind {
+; CHECK-LABEL: remat_load:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: addi sp, sp, -208
+; CHECK-NEXT: sd ra, 200(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s0, 192(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s1, 184(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s2, 176(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s3, 168(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s4, 160(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s5, 152(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s6, 144(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s7, 136(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s8, 128(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s9, 120(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s10, 112(sp) # 8-byte Folded Spill
+; CHECK-NEXT: sd s11, 104(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs0, 96(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs1, 88(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs2, 80(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs3, 72(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs4, 64(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs5, 56(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs6, 48(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs7, 40(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs8, 32(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs9, 24(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs10, 16(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fsd fs11, 8(sp) # 8-byte Folded Spill
+; CHECK-NEXT: fld fa5, 264(sp)
+; CHECK-NEXT: flw fa4, 256(sp)
+; CHECK-NEXT: flh fa3, 248(sp)
+; CHECK-NEXT: flh fa2, 240(sp)
+; CHECK-NEXT: ld a0, 272(sp)
+; CHECK-NEXT: lbu a4, 208(sp)
+; CHECK-NEXT: lh a3, 216(sp)
+; CHECK-NEXT: lw a2, 224(sp)
+; CHECK-NEXT: ld a1, 232(sp)
+; CHECK-NEXT: sb a4, 0(a0)
+; CHECK-NEXT: sh a3, 0(a0)
+; CHECK-NEXT: sw a2, 0(a0)
+; CHECK-NEXT: sd a1, 0(a0)
+; CHECK-NEXT: fsh fa2, 0(a0)
+; CHECK-NEXT: fsh fa3, 0(a0)
+; CHECK-NEXT: fsw fa4, 0(a0)
+; CHECK-NEXT: fsd fa5, 0(a0)
+; CHECK-NEXT: #APP
+; CHECK-NEXT: #NO_APP
+; CHECK-NEXT: ld a0, 272(sp)
+; CHECK-NEXT: lbu a1, 208(sp)
+; CHECK-NEXT: sb a1, 0(a0)
+; CHECK-NEXT: lh a1, 216(sp)
+; CHECK-NEXT: sh a1, 0(a0)
+; CHECK-NEXT: lw a1, 224(sp)
+; CHECK-NEXT: sw a1, 0(a0)
+; CHECK-NEXT: ld a1, 232(sp)
+; CHECK-NEXT: sd a1, 0(a0)
+; CHECK-NEXT: flh fa5, 240(sp)
+; CHECK-NEXT: fsh fa5, 0(a0)
+; CHECK-NEXT: flh fa5, 248(sp)
+; CHECK-NEXT: fsh fa5, 0(a0)
+; CHECK-NEXT: flw fa5, 256(sp)
+; CHECK-NEXT: fsw fa5, 0(a0)
+; CHECK-NEXT: fld fa5, 264(sp)
+; CHECK-NEXT: fsd fa5, 0(a0)
+; CHECK-NEXT: ld ra, 200(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s0, 192(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s1, 184(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s2, 176(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s3, 168(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s4, 160(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s5, 152(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s6, 144(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s7, 136(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s8, 128(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s9, 120(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s10, 112(sp) # 8-byte Folded Reload
+; CHECK-NEXT: ld s11, 104(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs0, 96(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs1, 88(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs2, 80(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs3, 72(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs4, 64(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs5, 56(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs6, 48(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs7, 40(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs8, 32(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs9, 24(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs10, 16(sp) # 8-byte Folded Reload
+; CHECK-NEXT: fld fs11, 8(sp) # 8-byte Folded Reload
+; CHECK-NEXT: addi sp, sp, 208
+; CHECK-NEXT: ret
+entry:
+ ; Force loading the stack arguments to create their live interval
+ store volatile i8 %stackarg0, ptr %p
+ store volatile i16 %stackarg1, ptr %p
+ store volatile i32 %stackarg2, ptr %p
+ store volatile i64 %stackarg3, ptr %p
+ store volatile half %stackarg4, ptr %p
+ store volatile bfloat %stackarg5, ptr %p
+ store volatile float %stackarg6, ptr %p
+ store volatile double %stackarg7, ptr %p
+ tail call void asm sideeffect "", "~{x1},~{x3},~{x4},~{x5},~{x6},~{x7},~{x8},~{x9},~{x10},~{x11},~{x12},~{x13},~{x14},~{x15},~{x16},~{x17},~{x18},~{x19},~{x20},~{x21},~{x22},~{x23},~{x24},~{x25},~{x26},~{x27},~{x28},~{x29},~{x30},~{x31},~{f0},~{f1},~{f2},~{f3},~{f4},~{f5},~{f6},~{f7},~{f8},~{f9},~{f10},~{f11},~{f12},~{f13},~{f14},~{f15},~{f16},~{f17},~{f18},~{f19},~{f20},~{f21},~{f22},~{f23},~{f24},~{f25},~{f26},~{f27},~{f28},~{f29},~{f30},~{f31}"()
+ ; Now use them after spilling everything to force rematerialization
+ store volatile i8 %stackarg0, ptr %p
+ store volatile i16 %stackarg1, ptr %p
+ store volatile i32 %stackarg2, ptr %p
+ store volatile i64 %stackarg3, ptr %p
+ store volatile half %stackarg4, ptr %p
+ store volatile bfloat %stackarg5, ptr %p
+ store volatile float %stackarg6, ptr %p
+ store volatile double %stackarg7, ptr %p
+ ret void
+}
+
+; We could remat the load of the constant global if we extended the live
+; interval of the high bits of the address.
+
+ at const = constant i32 42
----------------
lukel97 wrote:
Good point, changed to a external constant in 86ddeeb8c24c574dcb38a22450d4eb6d1cc3a395. Looks like `EarlyCSEPass` handles the folding in the middle end, so these llc tests wouldn't pick it up.
https://github.com/llvm/llvm-project/pull/166774
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