[IR] Do not combine ptrtoaddr and trunc

The ptrtoaddr result type is required to match the pointer address
width. This means that, unlikely with ptrtoint, it's not legal to
merge a ptrtoint and trunc. This previously resulted in an IR
verifier failure.

Author: nikic

llvm/lib/IR/Instructions.cpp

@@ -2878,7 +2878,7 @@ unsigned CastInst::isEliminableCastPair(Instruction::CastOps firstOp,
     { 99,99,99, 0, 0,99,99, 0, 0,99,99,99, 4, 0}, // FPTrunc        |
     { 99,99,99, 2, 2,99,99, 8, 2,99,99,99, 4, 0}, // FPExt          |
     {  1, 0, 0,99,99, 0, 0,99,99,99,99, 7, 3, 0}, // PtrToInt       |
-    {  1, 0, 0,99,99, 0, 0,99,99,99,99, 0, 3, 0}, // PtrToAddr      |
+    {  0, 0, 0,99,99, 0, 0,99,99,99,99, 0, 3, 0}, // PtrToAddr      |
     { 99,99,99,99,99,99,99,99,99,11,11,99,15, 0}, // IntToPtr       |
     {  5, 5, 5, 0, 0, 5, 5, 0, 0,16,16, 5, 1,14}, // BitCast        |
     {  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,13,12}, // AddrSpaceCast -+

llvm/test/Transforms/InstCombine/ptrtoaddr.ll

@@ -0,0 +1,42 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt -S -passes=instcombine < %s | FileCheck %s
+
+; The ptrtoaddr folds are also valid for pointers that have external state.
+target datalayout = "pe1:64:64:64:32"
+
+; ptrtoaddr result type is fixed, and can't be combined with integer cast.
+define i32 @ptrtoaddr_trunc(ptr %p) {
+; CHECK-LABEL: define i32 @ptrtoaddr_trunc(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT:    [[P_ADDR:%.*]] = ptrtoaddr ptr [[P]] to i64
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i64 [[P_ADDR]] to i32
+; CHECK-NEXT:    ret i32 [[TRUNC]]
+;
+  %p.addr = ptrtoaddr ptr %p to i64
+  %trunc = trunc i64 %p.addr to i32
+  ret i32 %trunc
+}
+
+define i128 @ptrtoaddr_zext(ptr %p) {
+; CHECK-LABEL: define i128 @ptrtoaddr_zext(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT:    [[P_ADDR:%.*]] = ptrtoaddr ptr [[P]] to i64
+; CHECK-NEXT:    [[EXT:%.*]] = zext i64 [[P_ADDR]] to i128
+; CHECK-NEXT:    ret i128 [[EXT]]
+;
+  %p.addr = ptrtoaddr ptr %p to i64
+  %ext = zext i64 %p.addr to i128
+  ret i128 %ext
+}
+
+define i128 @ptrtoaddr_sext(ptr %p) {
+; CHECK-LABEL: define i128 @ptrtoaddr_sext(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT:    [[P_ADDR:%.*]] = ptrtoaddr ptr [[P]] to i64
+; CHECK-NEXT:    [[EXT:%.*]] = sext i64 [[P_ADDR]] to i128
+; CHECK-NEXT:    ret i128 [[EXT]]
+;
+  %p.addr = ptrtoaddr ptr %p to i64
+  %ext = sext i64 %p.addr to i128
+  ret i128 %ext
+}