- %tmp = load i16* %arrayidx, align 4, !tbaa !0
- %0 = icmp eq i16 %tmp, 17791
- br i1 %0, label %land.lhs.true9, label %if.end
-
-with this patch:
-Index: InstCombine/InstCombineCompares.cpp
-===================================================================
---- InstCombine/InstCombineCompares.cpp (revision 129500)
-+++ InstCombine/InstCombineCompares.cpp (working copy)
-@@ -2506,6 +2506,18 @@
- return &I;
- }
- }
-+
-+ // Transform "icmp eq (trunc X), cst" to "icmp (and X, mask), cst"
-+ if (Op0->hasOneUse() && match(Op0, m_Trunc(m_Value(A))) &&
-+ isa<ConstantInt>(Op1)) {
-+ APInt MaskV = APInt::getLowBitsSet(A->getType()->getPrimitiveSizeInBits(),
-+ Op0->getType()->getPrimitiveSizeInBits());
-+ Value *Mask =
-+ Builder->CreateAnd(A, ConstantInt::get(A->getContext(), MaskV));
-+ return new ICmpInst(I.getPredicate(), Mask,
-+ ConstantExpr::getZExt(cast<ConstantInt>(Op1),
-+ Mask->getType()));
-+ }
- }
-
- {
+t1 s1;
+t2 s2;
+
+void func1(void)
+{
+s1.f1 = s2.f1;
+s1.f2 = s2.f2;
+}
+
+Compiles into this IR (on x86-64 at least):
+
+%struct.t1 = type { i8, [3 x i8] }
+@s2 = global %struct.t1 zeroinitializer, align 4
+@s1 = global %struct.t1 zeroinitializer, align 4
+define void @func1() nounwind ssp noredzone {
+entry:
+ %0 = load i32* bitcast (%struct.t1* @s2 to i32*), align 4
+ %bf.val.sext5 = and i32 %0, 1
+ %1 = load i32* bitcast (%struct.t1* @s1 to i32*), align 4
+ %2 = and i32 %1, -4
+ %3 = or i32 %2, %bf.val.sext5
+ %bf.val.sext26 = and i32 %0, 2
+ %4 = or i32 %3, %bf.val.sext26
+ store i32 %4, i32* bitcast (%struct.t1* @s1 to i32*), align 4
+ ret void
+}
+
+The two or/and's should be merged into one each.
+
+//===---------------------------------------------------------------------===//
+
+Machine level code hoisting can be useful in some cases. For example, PR9408
+is about: