[clang] [clang] Add support for -fcx-limited-range and #pragma CX_LIMITED_RANGE. (PR #68820)

[Joshua Cranmer via cfe-commits]

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@@ -846,6 +865,105 @@ ComplexPairTy ComplexExprEmitter::EmitBinMul(const BinOpInfo &Op) {
   return ComplexPairTy(ResR, ResI);
 }
 
+ComplexPairTy ComplexExprEmitter::EmitAlgebraicDiv(llvm::Value *LHSr,
+                                                   llvm::Value *LHSi,
+                                                   llvm::Value *RHSr,
+                                                   llvm::Value *RHSi) {
+  // (a+ib) / (c+id) = ((ac+bd)/(cc+dd)) + i((bc-ad)/(cc+dd))
+  llvm::Value *DSTr, *DSTi;
+
+  llvm::Value *AC = Builder.CreateFMul(LHSr, RHSr); // a*c
+  llvm::Value *BD = Builder.CreateFMul(LHSi, RHSi); // b*d
+  llvm::Value *ACpBD = Builder.CreateFAdd(AC, BD);  // ac+bd
+
+  llvm::Value *CC = Builder.CreateFMul(RHSr, RHSr); // c*c
+  llvm::Value *DD = Builder.CreateFMul(RHSi, RHSi); // d*d
+  llvm::Value *CCpDD = Builder.CreateFAdd(CC, DD);  // cc+dd
+
+  llvm::Value *BC = Builder.CreateFMul(LHSi, RHSr); // b*c
+  llvm::Value *AD = Builder.CreateFMul(LHSr, RHSi); // a*d
+  llvm::Value *BCmAD = Builder.CreateFSub(BC, AD);  // bc-ad
+
+  DSTr = Builder.CreateFDiv(ACpBD, CCpDD);
+  DSTi = Builder.CreateFDiv(BCmAD, CCpDD);
+  return ComplexPairTy(DSTr, DSTi);
+}
+
+/// EmitFAbs - Emit a call to @llvm.fabs.
+static llvm::Value *EmitllvmFAbs(CodeGenFunction &CGF, llvm::Value *Value) {
+  llvm::Function *Func =
+      CGF.CGM.getIntrinsic(llvm::Intrinsic::fabs, Value->getType());
+  llvm::Value *Call = CGF.Builder.CreateCall(Func, Value);
+  return Call;
+}
+
+ComplexPairTy ComplexExprEmitter::EmitRangeReductionDiv(llvm::Value *LHSr,
+                                                        llvm::Value *LHSi,
+                                                        llvm::Value *RHSr,
+                                                        llvm::Value *RHSi) {
+  // (a + ib) / (c + id) = (e + if)
+  llvm::Value *FAbsRHSr = EmitllvmFAbs(CGF, RHSr); // |c|
+  llvm::Value *FAbsRHSi = EmitllvmFAbs(CGF, RHSi); // |d|
+  // |c| >= |d|
+  llvm::Value *IsR = Builder.CreateFCmpUGT(FAbsRHSr, FAbsRHSi, "abs_cmp");
+
+  llvm::BasicBlock *TrueBB = CGF.createBasicBlock("true_bb_name");
+  llvm::BasicBlock *FalseBB = CGF.createBasicBlock("false_bb_name");
+  llvm::BasicBlock *ContBB = CGF.createBasicBlock("cont_bb");
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jcranmer-intel wrote:

These could use better basic block names.

https://github.com/llvm/llvm-project/pull/68820