Add a regression test for mlir-stage-15-v1

This adds one LIT test covering 0 lines and 6 branch outcomes that the existing suite does not reach, across 1 source file, at 48615bc5925ef4b9db8b4550b5d4322933cf4b7b.

Coverage this test adds

Source file	Newly covered lines	Newly covered branch outcomes
lib/Frontend/Raising/ExactStandardSpelling.h	—	125:9–125:47 false; 131:9–131:40 false; 57:10–57:50 true; 58:10–58:49 true; 59:10–59:48 true; 60:10–60:47 true

The test

The input is 25 lines; reduction found nothing further to remove that kept the coverage above and a compiler that still accepted it. The CHECK lines are the compiler's exact output on this input at 48615bc5925ef4b9db8b4550b5d4322933cf4b7b.

// RUN: loom-raise-opt --loom-materialize-fmuladd=shape=fused %s | FileCheck %s

llvm.func @envelope_0(%x: f32, %y: f32, %z: f32) -> f32
    attributes {fp_contract = "off"} {
  %r0 = llvm.intr.fmuladd(%x, %y, %z) {fastmathFlags = #llvm.fastmath<fast>} : (f32, f32, f32) -> f32
  %r1 = llvm.intr.fmuladd(%r0, %y, %z) {fastmathFlags = #llvm.fastmath<fast>} : (f32, f32, f32) -> f32
  llvm.return %r1 : f32
}

func.func @native_1(%x: f64, %y: f64, %z: f64) -> f64 {
  %r0 = llvm.intr.fmuladd(%x, %y, %z) : (f64, f64, f64) -> f64
  return %r0 : f64
}

llvm.func @typed_2(%x: f64, %y: f64, %z: f64) -> f64 {
  %r0 = llvm.intr.fmuladd(%x, %y, %z) : (f64, f64, f64) -> f64
  %r1 = llvm.intr.fmuladd(%r0, %y, %z) : (f64, f64, f64) -> f64
  llvm.return %r1 : f64
}

llvm.func @envelope_3(%x: f32, %y: f32, %z: f32) -> f32
    attributes {denormal_fpenv = #llvm.denormal_fpenv<default_output_mode = ieee, default_input_mode = ieee, float_output_mode = ieee, float_input_mode = ieee>} {
  %r0 = llvm.intr.fmuladd(%x, %y, %z) : (f32, f32, f32) -> f32
  %r1 = llvm.intr.fmuladd(%r0, %y, %z) : (f32, f32, f32) -> f32
  llvm.return %r1 : f32
}


// CHECK: module {
// CHECK-NEXT:   llvm.func @envelope_0(%arg0: f32, %arg1: f32, %arg2: f32) -> f32 attributes {fp_contract = "off"} {
// CHECK-NEXT:     %0 = math.fma %arg0, %arg1, %arg2 fastmath<fast> : f32
// CHECK-NEXT:     %1 = math.fma %0, %arg1, %arg2 fastmath<fast> : f32
// CHECK-NEXT:     llvm.return %1 : f32
// CHECK-NEXT:   }
// CHECK-NEXT:   func.func @native_1(%arg0: f64, %arg1: f64, %arg2: f64) -> f64 {
// CHECK-NEXT:     %0 = math.fma %arg0, %arg1, %arg2 : f64
// CHECK-NEXT:     return %0 : f64
// CHECK-NEXT:   }
// CHECK-NEXT:   llvm.func @typed_2(%arg0: f64, %arg1: f64, %arg2: f64) -> f64 {
// CHECK-NEXT:     %0 = math.fma %arg0, %arg1, %arg2 : f64
// CHECK-NEXT:     %1 = math.fma %0, %arg1, %arg2 : f64
// CHECK-NEXT:     llvm.return %1 : f64
// CHECK-NEXT:   }
// CHECK-NEXT:   llvm.func @envelope_3(%arg0: f32, %arg1: f32, %arg2: f32) -> f32 attributes {denormal_fpenv = #llvm.denormal_fpenv<default_output_mode = ieee, default_input_mode = ieee, float_output_mode = ieee, float_input_mode = ieee>} {
// CHECK-NEXT:     %0 = math.fma %arg0, %arg1, %arg2 : f32
// CHECK-NEXT:     %1 = math.fma %0, %arg1, %arg2 : f32
// CHECK-NEXT:     llvm.return %1 : f32
// CHECK-NEXT:   }
// CHECK-NEXT: }
// CHECK-EMPTY:

Validation

• Native compiler and FileCheck replay: passed at 48615bc5925ef4b9db8b4550b5d4322933cf4b7b.
• Property checker verdict on the reduced pair: PASS (postcondition.spct, SHA-256 32c2f1137fecabff3bcd614b253f87a8b83c567b0b3388187885ee0a1c0a5e59).
• Reduction criterion: accepted checker PASS and every original line/branch increment over the suite baseline; the original postcondition BDD decision path is unchanged; every original fast edge increment over its suite baseline.

Where this test came from

PBT mlir-stage-15-v1, run 20260911-084459, seed 550.

The property under test is anchored on documentation:

• selected output: docs/spec-compiler-part-2-scf.md lines 185–186 (output side)
• linked input 61: docs/spec-compiler-part-2-scf.md lines 1018–1021 (input side)
• linked input 101: docs/spec-compiler-part-2-scf.md lines 178–181 (input side)
• linked input 127: docs/spec-compiler-part-2-scf.md lines 1021–1022 (input side)
• linked input 165: docs/spec-compiler-part-2-scf.md lines 1029–1034 (input side)
• linked input 209: docs/spec-compiler-part-2-scf.md lines 181–185 (input side)

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Coverage is measured against the recorded baseline suite at this revision, and counts unique mapped file locations including generated code. Reduction retains every added line or branch outcome and a passing property check; it is not a claim of global minimality, nor of a defect.