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[SystemZ] Allow forming overflow op for i128 #153557

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Merged
nikic merged 3 commits into from
Aug 14, 2025
Merged

[SystemZ] Allow forming overflow op for i128 #153557

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9603b72
add tests
nikic Aug 14, 2025
56c3d37
Allow forming overflow op for i128
nikic Aug 14, 2025
6ea88ca
Add check lines without z13
nikic Aug 14, 2025
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2 changes: 1 addition & 1 deletion llvm/lib/Target/SystemZ/SystemZISelLowering.h
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Expand Up @@ -523,7 +523,7 @@ class SystemZTargetLowering : public TargetLowering {
bool MathUsed) const override {
// Form add and sub with overflow intrinsics regardless of any extra
// users of the math result.
return VT == MVT::i32 || VT == MVT::i64;
return VT == MVT::i32 || VT == MVT::i64 || VT == MVT::i128;
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@uweigand uweigand Aug 14, 2025

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That looks fine for z13 and higher, but on older machines, i128 is not actually a legal type, and we have no instructions for 128-bit operflowing ops. The common code shouldFormOverflowOp has a !isOperationExpand(Opcode, VT) check - I think we need that here for the i128 case.

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@nikic nikic Aug 14, 2025

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I pushed additional check lines without z13. And here is the diff on top if we only do this for legal types: https://gist.github.com/nikic/6f84e1c7090a8c356f93e27fe0023a62

It looks like forming uaddo still results in a much better expansion even if we don't have legal i128. For usubo we get the same expansion either way (possibly there is a missed optimization opportunity in there?)

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@uweigand uweigand Aug 14, 2025

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Huh, OK. That looks good then. Thanks!

}

bool shouldConsiderGEPOffsetSplit() const override { return true; }
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13 changes: 8 additions & 5 deletions llvm/test/CodeGen/SystemZ/atomicrmw-ops-i128.ll
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Expand Up @@ -363,10 +363,11 @@ define i128 @atomicrmw_uinc_wrap(ptr %src, i128 %b) {
define i128 @atomicrmw_udec_wrap(ptr %src, i128 %b) {
; CHECK-LABEL: atomicrmw_udec_wrap:
; CHECK: # %bb.0:
; CHECK-NEXT: larl %r1, .LCPI12_0
; CHECK-NEXT: vl %v0, 0(%r4), 3
; CHECK-NEXT: vl %v3, 0(%r3), 4
; CHECK-NEXT: vgbm %v1, 65535
; CHECK-NEXT: vgbm %v2, 0
; CHECK-NEXT: vl %v1, 0(%r1), 3
; CHECK-NEXT: vgbm %v2, 65535
; CHECK-NEXT: j .LBB12_2
; CHECK-NEXT: .LBB12_1: # %atomicrmw.start
; CHECK-NEXT: # in Loop: Header=BB12_2 Depth=1
Expand All @@ -379,6 +380,9 @@ define i128 @atomicrmw_udec_wrap(ptr %src, i128 %b) {
; CHECK-NEXT: je .LBB12_8
; CHECK-NEXT: .LBB12_2: # %atomicrmw.start
; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
; CHECK-NEXT: vscbiq %v4, %v3, %v1
; CHECK-NEXT: vlgvf %r0, %v4, 3
; CHECK-NEXT: xilf %r0, 1
; CHECK-NEXT: veclg %v0, %v3
; CHECK-NEXT: jlh .LBB12_4
; CHECK-NEXT: # %bb.3: # %atomicrmw.start
Expand All @@ -390,12 +394,11 @@ define i128 @atomicrmw_udec_wrap(ptr %src, i128 %b) {
; CHECK-NEXT: jl .LBB12_6
; CHECK-NEXT: # %bb.5: # %atomicrmw.start
; CHECK-NEXT: # in Loop: Header=BB12_2 Depth=1
; CHECK-NEXT: vaq %v4, %v3, %v1
; CHECK-NEXT: vaq %v4, %v3, %v2
; CHECK-NEXT: .LBB12_6: # %atomicrmw.start
; CHECK-NEXT: # in Loop: Header=BB12_2 Depth=1
; CHECK-NEXT: vceqgs %v5, %v3, %v2
; CHECK-NEXT: vlr %v5, %v0
; CHECK-NEXT: je .LBB12_1
; CHECK-NEXT: cijlh %r0, 0, .LBB12_1
; CHECK-NEXT: # %bb.7: # %atomicrmw.start
; CHECK-NEXT: # in Loop: Header=BB12_2 Depth=1
; CHECK-NEXT: vlr %v5, %v4
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28 changes: 28 additions & 0 deletions llvm/test/CodeGen/SystemZ/int-cmp-65.ll
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Expand Up @@ -85,3 +85,31 @@ define i128 @i128_addc_4(i128 %a, i128 %b) {
ret i128 %ext
}

define i128 @i128_addc_xor(i128 %a, i128 %b) {
; CHECK-LABEL: i128_addc_xor:
; CHECK: # %bb.0:
; CHECK-NEXT: vl %v0, 0(%r3), 3
; CHECK-NEXT: vl %v1, 0(%r4), 3
; CHECK-NEXT: vaccq %v0, %v1, %v0
; CHECK-NEXT: vst %v0, 0(%r2), 3
; CHECK-NEXT: br %r14
%b.not = xor i128 %b, -1
%cmp = icmp ugt i128 %a, %b.not
%ext = zext i1 %cmp to i128
ret i128 %ext
}

define i128 @i128_addc_xor_inv(i128 %a, i128 %b) {
; CHECK-LABEL: i128_addc_xor_inv:
; CHECK: # %bb.0:
; CHECK-NEXT: vl %v1, 0(%r4), 3
; CHECK-NEXT: vl %v0, 0(%r3), 3
; CHECK-NEXT: vno %v1, %v1, %v1
; CHECK-NEXT: vscbiq %v0, %v1, %v0
; CHECK-NEXT: vst %v0, 0(%r2), 3
; CHECK-NEXT: br %r14
%b.not = xor i128 %b, -1
%cmp = icmp ule i128 %a, %b.not
%ext = zext i1 %cmp to i128
ret i128 %ext
}
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