[SROA] When unfolding gep of phi, insert gep into predecessor

Instead of inserting all the geps into the entry block, insert
them into the corresponding phi predecessor.

Author: nikic

llvm/lib/Transforms/Scalar/SROA.cpp

@@ -4123,7 +4123,6 @@ class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> {
     Type *SourceTy = GEPI.getSourceElementType();
     // We only handle arguments, constants, and static allocas here, so we can
     // insert GEPs at the end of the entry block.
-    IRB.SetInsertPoint(GEPI.getFunction()->getEntryBlock().getTerminator());
     for (unsigned I = 0, E = Phi->getNumIncomingValues(); I != E; ++I) {
       Value *Op = Phi->getIncomingValue(I);
       BasicBlock *BB = Phi->getIncomingBlock(I);
@@ -4132,6 +4131,7 @@ class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> {
         NewGEP = NewPhi->getIncomingValue(NI);
       } else {
         SmallVector<Value *> NewOps = GetNewOps(Op);
+        IRB.SetInsertPoint(BB->getTerminator());
         NewGEP =
             IRB.CreateGEP(SourceTy, NewOps[0], ArrayRef(NewOps).drop_front(),
                           Phi->getName() + ".sroa.gep", GEPI.getNoWrapFlags());

llvm/test/Transforms/SROA/phi-and-select.ll

@@ -767,14 +767,14 @@ define void @PR20822(i1 %c1, i1 %c2, ptr %ptr) {
 ; CHECK-LABEL: @PR20822(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[F_SROA_0:%.*]] = alloca i32, align 4
-; CHECK-NEXT:    [[F1_SROA_GEP:%.*]] = getelementptr inbounds [[STRUCT_S:%.*]], ptr [[PTR:%.*]], i32 0, i32 0
 ; CHECK-NEXT:    br i1 [[C1:%.*]], label [[IF_END:%.*]], label [[FOR_COND:%.*]]
 ; CHECK:       for.cond:
 ; CHECK-NEXT:    br label [[IF_END]]
 ; CHECK:       if.end:
 ; CHECK-NEXT:    [[TMP0:%.*]] = phi i32 [ poison, [[ENTRY:%.*]] ], [ poison, [[FOR_COND]] ]
 ; CHECK-NEXT:    br i1 [[C2:%.*]], label [[IF_THEN5:%.*]], label [[IF_THEN2:%.*]]
 ; CHECK:       if.then2:
+; CHECK-NEXT:    [[F1_SROA_GEP:%.*]] = getelementptr inbounds [[STRUCT_S:%.*]], ptr [[PTR:%.*]], i32 0, i32 0
 ; CHECK-NEXT:    br label [[IF_THEN5]]
 ; CHECK:       if.then5:
 ; CHECK-NEXT:    [[F1_SROA_PHI:%.*]] = phi ptr [ [[F1_SROA_GEP]], [[IF_THEN2]] ], [ [[F_SROA_0]], [[IF_END]] ]

llvm/test/Transforms/SROA/phi-gep.ll

@@ -644,9 +644,9 @@ define i1 @test_phi_mem2reg_entry_block_alloca_not_at_beginning(i1 %arg) {
 ; CHECK-NEXT:    call void @f()
 ; CHECK-NEXT:    [[ALLOCA:%.*]] = alloca i64, align 8
 ; CHECK-NEXT:    [[PHI_SROA_GEP:%.*]] = getelementptr i64, ptr [[ALLOCA]], i64 1
-; CHECK-NEXT:    [[PHI_SROA_GEP1:%.*]] = getelementptr i64, ptr [[ALLOCA]], i64 2
 ; CHECK-NEXT:    br i1 [[ARG:%.*]], label [[BB2:%.*]], label [[BB3:%.*]]
 ; CHECK:       bb2:
+; CHECK-NEXT:    [[PHI_SROA_GEP1:%.*]] = getelementptr i64, ptr [[ALLOCA]], i64 2
 ; CHECK-NEXT:    br label [[BB3]]
 ; CHECK:       bb3:
 ; CHECK-NEXT:    [[PHI_SROA_PHI:%.*]] = phi ptr [ [[PHI_SROA_GEP]], [[BB:%.*]] ], [ [[PHI_SROA_GEP1]], [[BB2]] ]
@@ -706,9 +706,9 @@ define i64 @test_unfold_phi_duplicate_phi_entry(ptr %arg, i8 %arg1, i1 %arg2) {
 ; CHECK-LABEL: @test_unfold_phi_duplicate_phi_entry(
 ; CHECK-NEXT:  bb:
 ; CHECK-NEXT:    [[ALLOCA_SROA_0:%.*]] = alloca i64, align 8
-; CHECK-NEXT:    [[PHI_SROA_GEP:%.*]] = getelementptr i64, ptr [[ARG:%.*]], i64 1
 ; CHECK-NEXT:    br i1 [[ARG2:%.*]], label [[BB5:%.*]], label [[BB3:%.*]]
 ; CHECK:       bb3:
+; CHECK-NEXT:    [[PHI_SROA_GEP:%.*]] = getelementptr i64, ptr [[ARG:%.*]], i64 1
 ; CHECK-NEXT:    switch i8 [[ARG1:%.*]], label [[BB4:%.*]] [
 ; CHECK-NEXT:      i8 0, label [[BB5]]
 ; CHECK-NEXT:      i8 1, label [[BB5]]