diff --git a/debian/changelog b/debian/changelog
index 9924d5ae..9cfe0d1a 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,8 +1,13 @@
 llvm-toolchain-10 (1:10.0.1-6) unstable; urgency=medium
 
+  [ Sylvestre Ledru ]
   * Add debian/* to the copyright file. Uses the same license
     as LLVM
 
+  [ Julien Cristau ]
+  * Cherry-pick "[PowerPC] PPCBoolRetToInt: Don't translate Constant's
+    operands".  Fixes rustc crash building firefox-esr.
+
  -- Sylvestre Ledru <sylvestre@debian.org>  Wed, 02 Sep 2020 13:55:46 +0200
 
 llvm-toolchain-10 (1:10.0.1-5) unstable; urgency=medium
diff --git a/debian/patches/PowerPC-PPCBoolRetToInt-Dont-translate-Constants-operands.diff b/debian/patches/PowerPC-PPCBoolRetToInt-Dont-translate-Constants-operands.diff
new file mode 100644
index 00000000..0f0cd41a
--- /dev/null
+++ b/debian/patches/PowerPC-PPCBoolRetToInt-Dont-translate-Constants-operands.diff
@@ -0,0 +1,96 @@
+From cbea17568f4301582c1d5d43990f089ca6cff522 Mon Sep 17 00:00:00 2001
+From: Kai Luo <lkail@cn.ibm.com>
+Date: Fri, 28 Aug 2020 01:56:12 +0000
+Subject: [PATCH] [PowerPC] PPCBoolRetToInt: Don't translate Constant's
+ operands
+
+When collecting `i1` values via `findAllDefs`, ignore Constant's
+operands, since Constant's operands might not be `i1`.
+
+Fixes https://bugs.llvm.org/show_bug.cgi?id=46923 which causes ICE
+```
+llvm-project/llvm/lib/IR/Constants.cpp:1924: static llvm::Constant *llvm::ConstantExpr::getZExt(llvm::Constant *, llvm::Type *, bool): Assertion `C->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits()&& "SrcTy must be smaller than DestTy for ZExt!"' failed.
+```
+
+Differential Revision: https://reviews.llvm.org/D85007
+---
+ llvm/lib/Target/PowerPC/PPCBoolRetToInt.cpp | 15 ++++++-----
+ llvm/test/CodeGen/PowerPC/pr46923.ll        | 29 +++++++++++++++++++++
+ 2 files changed, 38 insertions(+), 6 deletions(-)
+ create mode 100644 llvm/test/CodeGen/PowerPC/pr46923.ll
+
+diff --git a/llvm/lib/Target/PowerPC/PPCBoolRetToInt.cpp b/llvm/lib/Target/PowerPC/PPCBoolRetToInt.cpp
+index acc8b317a220..172f1346c507 100644
+--- a/llvm/lib/Target/PowerPC/PPCBoolRetToInt.cpp
++++ b/llvm/lib/Target/PowerPC/PPCBoolRetToInt.cpp
+@@ -78,9 +78,9 @@ class PPCBoolRetToInt : public FunctionPass {
+       Value *Curr = WorkList.back();
+       WorkList.pop_back();
+       auto *CurrUser = dyn_cast<User>(Curr);
+-      // Operands of CallInst are skipped because they may not be Bool type,
+-      // and their positions are defined by ABI.
+-      if (CurrUser && !isa<CallInst>(Curr))
++      // Operands of CallInst/Constant are skipped because they may not be Bool
++      // type. For CallInst, their positions are defined by ABI.
++      if (CurrUser && !isa<CallInst>(Curr) && !isa<Constant>(Curr))
+         for (auto &Op : CurrUser->operands())
+           if (Defs.insert(Op).second)
+             WorkList.push_back(Op);
+@@ -90,6 +90,9 @@ class PPCBoolRetToInt : public FunctionPass {
+ 
+   // Translate a i1 value to an equivalent i32/i64 value:
+   Value *translate(Value *V) {
++    assert(V->getType() == Type::getInt1Ty(V->getContext()) &&
++           "Expect an i1 value");
++
+     Type *IntTy = ST->isPPC64() ? Type::getInt64Ty(V->getContext())
+                                 : Type::getInt32Ty(V->getContext());
+ 
+@@ -252,9 +255,9 @@ class PPCBoolRetToInt : public FunctionPass {
+       auto *First = dyn_cast<User>(Pair.first);
+       auto *Second = dyn_cast<User>(Pair.second);
+       assert((!First || Second) && "translated from user to non-user!?");
+-      // Operands of CallInst are skipped because they may not be Bool type,
+-      // and their positions are defined by ABI.
+-      if (First && !isa<CallInst>(First))
++      // Operands of CallInst/Constant are skipped because they may not be Bool
++      // type. For CallInst, their positions are defined by ABI.
++      if (First && !isa<CallInst>(First) && !isa<Constant>(First))
+         for (unsigned i = 0; i < First->getNumOperands(); ++i)
+           Second->setOperand(i, BoolToIntMap[First->getOperand(i)]);
+     }
+diff --git a/llvm/test/CodeGen/PowerPC/pr46923.ll b/llvm/test/CodeGen/PowerPC/pr46923.ll
+new file mode 100644
+index 000000000000..3e9faa60422a
+--- /dev/null
++++ b/llvm/test/CodeGen/PowerPC/pr46923.ll
+@@ -0,0 +1,29 @@
++; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
++; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-unknown \
++; RUN:   -ppc-asm-full-reg-names < %s | FileCheck %s
++
++@bar = external constant i64, align 8
++
++define i1 @foo() {
++; CHECK-LABEL: foo:
++; CHECK:       # %bb.0: # %entry
++; CHECK-NEXT:    li r3, 0
++; CHECK-NEXT:    isel r3, 0, r3, 4*cr5+lt
++; CHECK-NEXT:    blr
++entry:
++  br label %next
++
++next:
++  br i1 undef, label %true, label %false
++
++true:
++  br label %end
++
++false:
++  br label %end
++
++end:
++  %a = phi i1 [ icmp ugt (i64 0, i64 ptrtoint (i64* @bar to i64)), %true ],
++              [ icmp ugt (i64 0, i64 2), %false ]
++  ret i1 %a
++}
diff --git a/debian/patches/series b/debian/patches/series
index 48789a1d..759e0195 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -147,3 +147,4 @@ ubuntu-groovy.diff
 clang_vendor_pass_stage2.diff
 remove-trailing-space-version.diff
 mips-force-nomadd4.patch
+PowerPC-PPCBoolRetToInt-Dont-translate-Constants-operands.diff